Calculators
741 free formula-based calculators across 16 categories. Step-by-step working shown alongside every result.
Every calculation. Explained.
741 free formula-based calculators across 16 categories. Every result shows the working — not just the answer.
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Math60
Pure-formula math calculators with step-by-step working shown alongside every result.
Percentage Math Calculator
Calculate what X% of a value is, find what percentage one number is of another, or compute the percentage change between two numbers.
Fraction to Decimal Calculator
Convert any fraction n/d to its decimal form, including detection of repeating decimals.
Decimal to Fraction Calculator
Convert a terminating decimal to its simplified fraction form.
Ratio Calculator & Simplifier
Simplify a ratio like 12:18 to its lowest terms (2:3) and compare to a target ratio.
Proportion Solver
Given a/b = c/x (or any of three knowns), solve for the fourth.
Mean (Average) Calculator
Compute the arithmetic mean of a list of numbers.
Median Calculator
Find the middle value (or average of two middle values) of a list of numbers.
Mode Calculator
Find the most frequently occurring value (or values) in a list.
Range Calculator
Compute the range (max − min) of a list of numbers.
Logarithm Calculator
log_b(x) for any base b > 0, b ≠ 1, x > 0. Common bases shown side-by-side.
Antilogarithm Calculator
b^x — the inverse of a logarithm. Given the log value and base, recover the original number.
Exponential Growth Calculator
A = A₀ · e^(kt) for continuous growth, or A = A₀ · (1 + r)^t for discrete.
Exponential Decay Calculator
A = A₀ · e^(-kt). Compute remaining quantity, half-life, or decay constant.
Continuous Compounding Calculator
A = P · e^(rt) — the limit of compound interest as the compounding frequency → ∞.
GCD (Greatest Common Divisor) Calculator
Euclidean algorithm: gcd(a,b) = gcd(b, a mod b). Supports 2-6 integers.
LCM (Least Common Multiple) Calculator
lcm(a,b) = |a × b| / gcd(a,b). Smallest number that both a and b divide evenly.
Prime Number Checker
Is n prime? Trial division up to √n; identifies smallest divisor and nearest primes if composite.
Prime Factorization Calculator
n = p₁^a₁ × p₂^a₂ × … Trial division to find all prime factors with multiplicity.
Factorial Calculator (n!)
n! = 1 × 2 × … × n. Computes exactly up to 21! (number limit); approximate via Stirling for larger.
Scientific Notation Converter
Convert decimal ↔ scientific notation. Standard form a × 10^b with 1 ≤ |a| < 10.
Square Root Calculator (√n)
√n with integer-perfect-square check, simplified surd form, and decimal expansion.
Cube Root Calculator (∛n)
∛n with perfect-cube detection, simplified surd form, and decimal expansion.
Nth Root Calculator
ⁿ√x = x^(1/n). Generalizes square and cube roots to any positive integer n.
Exponent Calculator (b^x)
b^x — supports fractional, negative, and zero exponents.
Geometry41
Area, perimeter, and volume calculators for every common 2D shape and 3D solid.
Area of a Circle Calculator
Calculate the area of a circle given its radius (or diameter). A = πr².
Area of a Square Calculator
A = s² where s is the side length.
Area of a Rectangle Calculator
A = length × width.
Area of a Triangle Calculator
Three formulas: base × height ÷ 2, SAS (two sides and angle), and Heron's (three sides).
Area of a Trapezoid Calculator
A = ½ × (parallel side a + parallel side b) × height.
Area of a Parallelogram Calculator
A = base × height (perpendicular height).
Area of a Rhombus Calculator
A = (d₁ × d₂) / 2 — half the product of the diagonals.
Area of an Ellipse Calculator
A = π × a × b, where a and b are the semi-major and semi-minor axes.
Area of a Circular Sector Calculator
A = ½ r² θ (radians) or A = πr² × (θ/360) (degrees).
Area of a Regular Polygon Calculator
A = ¼ × n × s² × cot(π/n) for an n-gon with side length s.
Rectangle Perimeter Calculator
P = 2(l + w). Length plus width, doubled.
Square Perimeter Calculator
P = 4s. Four equal sides.
Triangle Perimeter Calculator
P = a + b + c. Sum of all three sides.
Trapezoid Perimeter Calculator
P = a + b + c + d. Sum of two parallel sides + two non-parallel.
Circle Circumference Calculator
C = 2πr (or πd). Area = πr². The fundamental circle formulas.
Ellipse Perimeter Calculator (Ramanujan)
P ≈ π(a + b)(1 + 3h / (10 + √(4 − 3h))) where h = ((a−b)/(a+b))². Ramanujan approximation.
Cube Volume Calculator
V = s³. Six equal square faces.
Rectangular Prism Volume
V = l × w × h. Box / cuboid volume.
Sphere Volume Calculator
V = (4/3)πr³. Surface area = 4πr².
Cylinder Volume Calculator
V = πr²h. Surface area = 2πr² + 2πrh (top + bottom + side).
Cone Volume Calculator
V = (1/3)πr²h. One-third of the cylinder of same base and height.
Pyramid Volume Calculator
V = (1/3) × base area × height. For square / rectangular / triangular bases.
Cube Surface Area Calculator
SA = 6s². Six identical square faces.
Rectangular Prism Surface Area
SA = 2(lw + lh + wh). Box / cuboid surface.
Trigonometry21
Solve right and oblique triangles, evaluate trigonometric functions, and convert between degrees and radians.
Sine Calculator
Compute sin(x) for any angle in degrees or radians.
Cosine Calculator
Compute cos(x) for any angle.
Tangent Calculator
tan(x) = sin(x) / cos(x). Undefined where cos(x) = 0 (at 90°, 270°, …).
Arcsine Calculator
sin⁻¹(x) — find the angle whose sine is x. Domain [-1, 1], range [−90°, 90°].
Arccosine Calculator
cos⁻¹(x) — find the angle whose cosine is x. Range [0°, 180°].
Arctangent Calculator
tan⁻¹(x) — find the angle whose tangent is x. Range (−90°, 90°).
Degrees to Radians Converter
Convert any angle in degrees to radians. radians = degrees × π/180.
Radians to Degrees Converter
Convert any angle in radians to degrees. degrees = radians × 180/π.
Law of Sines Calculator
a/sin(A) = b/sin(B) = c/sin(C). Solve any triangle given AAS / ASA / SSA.
Law of Cosines Calculator
c² = a² + b² − 2ab·cos(C). Solve any triangle given SAS or SSS.
Right Triangle Solver
Given any 2 of (a, b, c, angle), solve all remaining sides + angles.
Unit Circle Calculator
Angle θ → (cos θ, sin θ) coordinates on the unit circle. Reference angle + quadrant.
Hyperbolic Sine Calculator (sinh)
sinh(x) = (eˣ − e⁻ˣ) / 2. Hyperbolic counterpart of sin.
Hyperbolic Cosine Calculator (cosh)
cosh(x) = (eˣ + e⁻ˣ) / 2. Catenary curve: y = a · cosh(x/a).
Hyperbolic Tangent Calculator (tanh)
tanh(x) = sinh(x) / cosh(x). Bounded between −1 and 1. Used in neural networks.
Angle of Elevation / Depression
tan(angle) = opposite / adjacent. Find angle from height + distance.
Distance to Object (Angle + Height)
distance = height / tan(angle). Range from observer to base of object.
Ladder Safe Angle (4:1 Rule)
For every 4 ft of height, base is 1 ft from wall. Angle ≈ 75.5°.
Roof Rafter Length
Rafter² = run² + rise². Pythagorean from pitch + run.
Satellite Dish Pointing (Az/El)
Approximate azimuth + elevation for geostationary satellite (101°W example).
Surveying Triangulation Distance
Given baseline + 2 angles, find unknown distance via law of sines.
Statistics & Probability33
Descriptive statistics and probability tools for datasets, distributions, and combinatorics.
Standard Deviation Calculator
Compute sample (n−1) and population (n) standard deviation from a list of numbers.
Variance Calculator
Sample (n−1) and population (n) variance — the square of standard deviation.
Percentile Calculator
Find the value at the kth percentile in a dataset (linear interpolation).
Z-Score Calculator
z = (x − μ) / σ — how many standard deviations a value is above or below the mean.
T-Score Calculator
t = (x̄ − μ₀) / (s/√n) — for testing a sample mean against a hypothesized population mean.
Interquartile Range (IQR) Calculator
IQR = Q3 − Q1 — the middle 50% spread, robust to outliers.
Coefficient of Variation (CV) Calculator
CV = σ / μ — relative variability as a percentage. Useful for comparing spread across different scales.
Geometric Mean Calculator
GM = (x₁ · x₂ · ... · xₙ)^(1/n). Right "average" for ratios, growth rates, multiplicative quantities.
Combinations Calculator C(n, r)
C(n, r) = n! / (r!(n−r)!). Number of ways to choose r items from n where order doesn't matter.
Permutations Calculator P(n, r)
P(n, r) = n! / (n−r)!. Number of ways to arrange r items from n where order matters.
P-Value Calculator (z to p)
Convert a z-score to one-tail or two-tail p-value via the standard normal CDF.
Confidence Interval Calculator
CI = mean ± z × (σ/√n). 90 / 95 / 99 % standard intervals.
Normal Distribution Calculator (PDF + CDF)
Compute probability density and cumulative probability at x for given μ, σ.
Binomial Probability Calculator
P(X = k) = C(n,k) p^k (1−p)^(n−k). Probability of exactly k successes in n trials.
Pearson Correlation Coefficient
r = Σ(xᵢ−x̄)(yᵢ−ȳ) / √(Σ(xᵢ−x̄)² Σ(yᵢ−ȳ)²). Linear correlation [−1, 1].
Two-Sample t-Test (Welch's)
Test whether two means differ. t = (x̄₁ − x̄₂) / √(s₁²/n₁ + s₂²/n₂).
One-Sample z-Test
z = (x̄ − μ) / (σ/√n). Compare sample mean to known population.
Chi-Square Goodness-of-Fit
χ² = Σ(O−E)²/E. Test if observed frequencies match expected.
One-Way ANOVA F-Statistic
F = MS_between / MS_within. Test if 3+ group means differ.
Linear Regression (Slope + Intercept)
y = mx + b via least squares. Returns m, b, r², SE.
Sample Size for Margin of Error
n = (z × σ / E)². Required sample size for given margin E at confidence z.
Mean, Median & Mode Calculator
Paste a list of numbers to get the mean, median, mode, range, count, and sum — the core measures of central tendency.
Standard Deviation Calculator
Compute sample and population standard deviation and variance from a pasted list of numbers, with the mean and formulas shown.
Quartile, IQR & Outlier Calculator
Find Q1, Q2 (median), Q3, the interquartile range, and outliers using the 1.5×IQR rule from a pasted dataset.
Science98
Formula calculators for classical mechanics, electricity, thermodynamics, and general chemistry.
Force Calculator (F = m·a)
Newton's second law: enter mass and acceleration, get force in newtons. Step-by-step working and pound-force conversion shown.
Work Done Calculator (W = F·d·cos θ)
Compute mechanical work from force, displacement, and the angle between them. Result in joules with calorie and foot-pound conversions.
Kinetic Energy Calculator (KE = ½·m·v²)
Compute the kinetic energy of a moving object from its mass and speed. Result in joules with kcal and ft·lb conversions.
Gravitational Potential Energy (PE = m·g·h)
Energy stored in an object lifted to a height. Enter mass, height, and (optionally) the gravity of another planet.
Momentum Calculator (p = m·v)
Compute linear momentum from mass and velocity. Result in kg·m/s, with a comparison to a typical small car at highway speed.
Impulse Calculator (J = F·Δt)
Compute impulse from force and contact time, or use it to find the change in velocity for a given mass.
Average Velocity Calculator (v = Δd/Δt)
Compute average velocity from total displacement and elapsed time. Result in m/s with km/h and mph conversions.
Ohm's Law Calculator (Extended)
V = IR, P = IV = I²R = V²/R. Pick which two values you know and solve for the others.
Electrical Power Calculator
P = IV — compute power from voltage and current, or from voltage and resistance, or current and resistance.
Electric Field Calculator
Compute electric field from a point charge: E = kQ/r², or from force/charge: E = F/q.
Capacitance Calculator
C = Q/V or parallel-plate C = ε₀A/d. Compute capacitance, charge stored, or energy.
Inductance Calculator
L = μ₀N²A/ℓ for an ideal solenoid, or V = L(dI/dt) for the defining equation.
RC Time Constant Calculator
τ = RC. Time for an RC circuit to charge to ~63% (or discharge to ~37%) of final value.
Parallel Resistance Calculator
1/R = 1/R₁ + 1/R₂ + … — find equivalent resistance of resistors in parallel.
Series Resistance Calculator
R_total = R₁ + R₂ + R₃ + … — find equivalent resistance of resistors in series.
Kirchhoff Voltage Loop Solver
Sum of voltages around a closed loop = 0. Solve a 2-loop circuit with two batteries and three resistors.
Molarity Calculator
M = moles solute / liters solution. The most common solution-concentration unit in chemistry.
Molality Calculator
m = moles solute / kg solvent. Used in colligative-property calculations (boiling-point elevation, freezing-point depression).
Molar Mass Calculator
Compute molar mass from a chemical formula. Supports common elements; multi-character symbols and subscripts.
Mole ↔ Gram Conversion
Convert between moles and grams using molar mass.
Dilution Calculator (M₁V₁ = M₂V₂)
Find target volume or concentration when diluting a stock solution.
pH Calculator (from [H⁺])
pH = -log[H⁺]. Compute pH from hydrogen-ion concentration in mol/L.
pH from pOH Calculator
pH + pOH = 14 at 25°C. Convert one to the other.
Percent Yield Calculator
Percent yield = (actual / theoretical) × 100. Quantifies reaction efficiency.
Date & Time44
Compute age, durations, deadlines, and working-day differences between any two dates.
Days Between Dates Calculator
Count the exact number of days between any two dates — all calendar days, weekdays only, or business days (skipping US federal holidays). Pick whether to include both endpoints or just the difference.
Weeks Between Dates Calculator
Calculate the number of weeks between two dates as a decimal, plus a whole-weeks-and-days breakdown.
Time Calculator — Add or Subtract Hours, Minutes, Seconds
Add or subtract two time values in HH:MM:SS form. Returns the result as HH:MM:SS, total decimal hours, and total seconds. Handles values longer than 24 hours.
Months Between Dates Calculator
Count whole calendar months between two dates, with the leftover days reported separately.
Years Between Dates Calculator
Compute years between two dates with a years/months/days breakdown — useful for tenure, anniversaries, and exact-age questions.
Detailed Age Calculator
Calculate age down to the second — years, months, days, hours, minutes, and seconds. Useful for milestones and trivia.
Date Add Calculator
Add days, weeks, months, or years to any date and get the resulting date — handles month-end clamping correctly.
Date Subtract Calculator
Subtract days, weeks, months, or years from a date — for things like "what date was 90 days ago?" or "5 years before today".
Week Number Calculator
Convert any date into its ISO 8601 week number, US week number, and day of the year.
Day of the Week Calculator
What day of the week was (or will be) any given date? Useful for historical curiosities and scheduling.
Leap Year Checker
Is a given year a leap year? Apply the Gregorian rule with a step-by-step explanation.
Gestation Age Calculator
Compute gestational age (weeks + days) from last menstrual period. Not medical advice.
Ovulation Window Predictor
Predicted ovulation date and fertile window from LMP and cycle length. Not medical advice.
Pregnancy Week & Trimester Calculator
Pregnancy week, trimester, and weeks-until-due from LMP. Not medical advice.
Menstrual Cycle Predictor
Predict the next 6 expected period start dates from a recent period and cycle length. Not medical advice.
Due Date from Conception Calculator
Estimated due date = conception + 266 days. Not medical advice.
Conception Date from Due Date
Estimated conception window = due date − 266 days, ± a few days for fertile window. Not medical advice.
Retirement Date Calculator
Compute your retirement date from date of birth and target retirement age.
Anniversary Calculator
Years celebrated, days to next, and traditional/modern gift suggestions.
Holiday Counter (US)
List US federal holidays for any year (2024-2030 hardcoded) with day-of-week.
Time Zone Converter
Convert a date+time from one IANA time zone to another.
Business Days Calculator
Count business days (Mon-Fri, excluding US federal holidays) between two dates.
Working Hours Calculator
Total work hours = business days × hours/day, optionally including weekends.
Hours Between Times Calculator
Compute hours and minutes between two HH:MM times, handling overnight wrap.
Construction99
Estimate materials, room dimensions, and project costs for residential and commercial construction.
Concrete Volume Calculator
Cubic yards of concrete for a rectangular slab/footing OR a cylindrical column/sonotube — with waste factor.
Concrete Bag Yield Calculator
Translate cubic feet of concrete into the number of pre-mix bags you need at 40, 60, or 80 lb per bag.
Mortar Bag Yield Calculator
How many bags of mortar are needed for a given brick or block count? Uses standard mortar-per-brick consumption.
Brick Count Calculator
How many bricks do you need for a wall? Enter dimensions, brick size, and joint thickness.
Rebar Spacing & Quantity Calculator
Linear feet of rebar needed for a slab grid, given dimensions and on-center spacing.
Gravel Volume Calculator
Cubic yards and tons of gravel for a driveway, base course, or landscape area.
Sand Volume Calculator
Cubic yards and tons of sand for a base, paver bed, or sandbox.
Mulch Volume Calculator
How many cubic yards or 2-cubic-foot bags of mulch do you need for a flowerbed or landscape area?
Topsoil Volume Calculator
Cubic yards and 40-lb bags of topsoil for a lawn renovation, garden bed, or fill area.
Asphalt Tonnage Calculator
Tons of hot-mix asphalt for a driveway or parking area, given dimensions and lift thickness.
Cement-Water Mix Ratio Calculator
How much water to add to a bag of cement for a target water-cement ratio (and matching aggregate volumes for a 1:2:3 mix).
Crushed Stone Coverage Calculator
How many cubic yards or tons of crushed stone for a driveway base, French drain, or landscape.
Interior Paint Quantity Calculator
Gallons needed — enter the wall area directly OR room dimensions (calculator subtracts doors/windows).
Exterior Paint Quantity Calculator
Exterior coverage typically 250-300 ft²/gal — rougher surfaces, porous siding.
Drywall Sheet Calculator
Sheets needed = wall area / sheet area (32 ft² for 4×8, 48 ft² for 4×12).
Lumber Board Feet Calculator
Board-feet = (thickness in × width in × length ft) / 12 × pieces.
Lumber Linear Feet Cost Calculator
Total = pieces × length × $/LF.
Framing Stud Count Calculator
Studs needed = wall length / spacing + corners + 10% waste.
Roofing Square Count Calculator
1 roofing square = 100 ft². Bundles = squares × 3 (for 3-tab) or × 4 (architectural).
Shingle Bundle Count Calculator
Bundles = roof area / coverage per bundle (33⅓ ft² for 3-tab).
Plywood Sheet Count Calculator
Sheets = surface area / 32 ft² (standard 4×8 sheet) + waste.
Ceiling Tile Count Calculator
Tiles = ceiling area / tile area, plus grid-feet for the suspended grid.
Fence Material Calculator
Posts, panels, and rails for a wood/vinyl/chain-link fence.
Deck Material Calculator
Decking boards, joists, posts, and fasteners for a residential deck.
Sports51
Performance, training, and scoring calculators across running, cycling, weightlifting, golf, and more.
Running Pace & Splits Calculator
Calculate pace per mile and per kilometer from any distance and finish time, with 5K/10K/half/marathon split projections.
Running Pace Converter (min/km ↔ min/mile)
Convert between minutes per kilometer and minutes per mile in either direction.
VDOT Calculator (Jack Daniels)
Compute your Jack Daniels VDOT score from a recent race time. VDOT is a single-number proxy for current running fitness.
McMillan Race Time Equivalents
Predict equivalent race times for other distances based on a recent race, using the McMillan exponent (similar to the Riegel formula).
Running Cadence Calculator
Convert between cadence (steps per minute), stride length, and running speed.
Finish Time from Pace Calculator
Predict your race finish time given a target pace and distance.
Race Time Predictor (Riegel formula)
Predict your time at any distance using Riegel's formula T₂ = T₁ × (D₂/D₁)^1.06.
Running Speed Zones (Z1-Z5)
Compute the five training-pace zones (recovery to VO₂max) from your lactate-threshold pace.
Cycling Power-to-Weight Calculator
W/kg = sustained power (W) / body weight (kg). Maps to USAC category and Coggan rider type.
FTP from 20-Minute Test Calculator
Functional Threshold Power = 20-min average power × 0.95. The standard cycling test protocol.
Cycling Pace / Time Calculator
Time = distance / speed. Convert any of {distance, speed, time} given the other two.
Cycling Calorie Burn by Power Calculator
kcal ≈ avg watts × hours × 3.6 — direct from work done (kJ ≈ kcal at 25% gross efficiency).
Bicycle Gear Ratio + Gear Inches Calculator
Ratio = front teeth / rear teeth. Gear inches = ratio × wheel diameter (in).
Gradient (Grade %) Calculator
Grade % = rise / run × 100. Convert to angle (degrees) and category (Cat 4-HC).
Swim Pace Per 100 Calculator
Swim pace per 100 m and per 100 yd from total distance and time.
Swim CSS (Critical Swim Speed) Calculator
CSS = (400m time − 200m time) / 200, in seconds per metre. Per Salo et al. — the swim equivalent of FTP.
Swim Stroke Count + SWOLF Calculator
SWOLF = stroke count + seconds for one pool length. Lower = more efficient.
Pool Laps for Distance Calculator
Laps = ⌈target distance / pool length⌉. Convert any target distance to laps in any pool.
One-Rep Max Calculator (Brzycki / Epley / Lombardi)
1RM from a sub-max set using Brzycki, Epley, and Lombardi formulas — three estimates side by side.
Wilks Score Calculator
Wilks score normalizes powerlifting total across bodyweight categories (men + women coefficients).
Barbell Plate Loading Calculator
Plate breakdown per side: 45 / 35 / 25 / 10 / 5 / 2.5 lb (or 25 / 20 / 15 / 10 / 5 / 2.5 / 1.25 kg).
Warm-up Set Percentages Calculator
Working set weight × {40%, 55%, 70%, 85%} → warm-up progression for the working set.
Training Volume Calculator
Volume = sets × reps × weight. Total tonnage moved per session, week, or block.
RPE to Percentage of 1RM Calculator
Map RPE 6-10 across 1-12 reps to % of 1RM (Tuchscherer / Reactive Training Systems table).
Cooking & Recipe73
Scale recipes, convert between volume and weight, and time roasts and bakes accurately.
Recipe Scaler
Scale a recipe up or down — multiply every ingredient by the ratio of target servings to original servings.
Recipe Serving Converter
Convert a recipe between any two serving sizes with examples for common ingredients.
Batch Baker Calculator
Recipe yields N items but you want M — find the batch multiplier.
Restaurant Portion Calculator
Convert a home-recipe yield (typically 4 entrée servings) to restaurant-portion counts (typically 5-6 oz mains).
Half Recipe Calculator
Halve a recipe — apply 0.5× to every ingredient, with notes for items that don't halve cleanly.
Double Recipe Calculator
Double a recipe — multiply every ingredient by 2, with notes on leavening, salt, and bake time.
Quarter Recipe Calculator
Quarter a recipe — divide everything by 4, with notes for fractional eggs and small-batch limits.
Ingredient Substitution Quantity
When swapping an ingredient for another, how much of the substitute do you use? Common ratios for sweeteners, fats, flours.
Partial Package Yield Calculator
Recipe expects a full package of ingredient X but you only have a partial — find what fraction of the recipe to make.
Leftover Yield Calculator
Recipe yielded N servings; you have S left. Compute the leftover percentage and meals remaining.
Cups to Grams Converter (Ingredient-Specific)
Cups → grams for flour, sugar, butter, oil, milk, water, brown sugar, oats, cocoa, and more — ingredient density matters.
Tablespoons to Grams Converter
Tablespoons → grams for common ingredients. 1 tbsp = ~14.8 mL volume; mass varies by density.
Ounces to Grams Converter (Weight)
Weight ounces ↔ grams. 1 oz = 28.3495 g exactly. Bidirectional.
Sticks of Butter to Cups / Tbsp / Grams
1 stick = ½ cup = 8 tbsp = 4 oz = 113 g. Convert any of those to the others.
Can Size Equivalents Calculator
Standard US can sizes: #303 = 16 oz, #2 = 20 oz, #2.5 = 28 oz, #10 = 109 oz. Convert by weight, cups, mL.
Produce Equivalents Calculator
Recipe says "1 lemon" or "1 medium onion"? Convert between count and tablespoons / cups.
Egg Size Equivalents Calculator
Recipe calls for X large eggs but you have medium / jumbo / extra-large? Convert by total egg-mass.
Oven Temperature °C ↔ °F Converter
Bidirectional °C ↔ °F conversion with common oven preset labels (low / medium / hot / very hot).
Fan vs Conventional Oven Temperature Converter
Fan-forced (convection) ovens cook ~25 °F (~14 °C) hotter than conventional. Convert in either direction.
UK Gas Mark to °F / °C Converter
Gas Mark 1 = 275 °F = 135 °C. Each mark adds ~25 °F (~14 °C). Modern UK ovens still use this scale.
Instant Pot to Stovetop Time Converter
Stovetop simmer time ≈ Instant Pot time × 3-4 (depending on the cut/category). Doesn't include IP pressurization time.
Slow Cooker to Instant Pot Time Converter
Slow-cooker hours → Instant Pot minutes. Typical compression 6-12×.
Baker's Percentage Calculator
Flour = 100%; every other ingredient as a % of flour by weight. Universal scaling for breads and doughs.
Sourdough Starter Feeding Calculator
X:Y:Z ratio starter:flour:water. Standard 1:1:1 for daily; 1:5:5 for slower fridge schedule.
Automotive29
Performance, ownership-cost, and tuning calculators for cars, trucks, and motorcycles.
Gas Mileage (MPG) Calculator
Compute miles per gallon from distance and gallons used. Also returns L/100km.
Trip Fuel Cost Calculator
Estimate fuel cost from trip distance, fuel economy, and price per unit. Toggle miles/km, MPG / km per L / L per 100 km, and $/gal vs $/L.
Miles Per Tank Calculator
Estimate how far you can drive on a full tank from MPG and tank capacity.
Average Speed Calculator
speed = distance / time. Pick units and read average speed in mph or km/h.
Distance Calculator (from speed and time)
distance = speed × time. Useful for "if I drive X mph for Y hours, how far?" questions.
Road Trip Time Calculator
How long will a road trip take? Distance / speed plus breaks and fuel stops.
Hours to Arrival Calculator
Given remaining distance and speed, when will you arrive?
Acceleration Calculator
a = (v_final − v_initial) / time. Useful for 0-60 times and physics problems.
Car Loan Payment Calculator
Auto loan payment via amortization. Principal, APR, term → monthly + total interest.
Lease vs Buy Car Comparison
Compare 36-mo lease total cost vs. 5-yr purchase + resale. Same out-of-pocket cash basis.
Car Affordability Calculator
Max car price = (monthly budget × loan factor) using 20/4/10 rule and DTI cap.
Car Depreciation Calculator
Straight-line or declining-balance depreciation. Most cars lose 15-25% year 1, 50%+ by year 5.
Total Cost of Ownership (Car)
Purchase + insurance + fuel + maintenance + depreciation over N years.
Oil Change Interval Calculator
Miles since last × interval-miles → next due date and miles. By oil type.
Brake Fluid Flush Cost Calculator
Fluid + labor cost. Recommended every 2 years or 30,000 miles.
Transmission Fluid Service Cost
Fluid + filter + labor cost for ATF service. Every 30-60k miles depending on type.
Cooling System Flush Cost
Coolant + thermostat (optional) + labor. Every 60-100k miles or 5 years.
Available Towing Capacity Calculator
Towing = GCWR − vehicle weight − passengers − payload. Stay 80% of max for safety.
Vehicle Gear Ratio (Final Drive) Calculator
RPM = (MPH × 336 × ratio) / tire-diameter. Find RPM at given speed for any axle ratio.
Tire Size Converter (P-Metric)
P-metric (215/65R16) → overall diameter, revolutions/mile, sidewall height.
Tire Pressure Adjustment by Temperature
Tire PSI changes ~1 psi per 10°F. Adjust for outdoor temp delta from setting temp.
Engine Displacement Converter
cc ↔ liters ↔ cubic inches. 1 L = 1000 cc; 1 cu in = 16.387 cc.
Horsepower to Torque Calculator
T (lb-ft) = 5252 × HP / RPM. The fundamental engine equation.
Torque to Horsepower Calculator
HP = T × RPM / 5252. Converts engine torque to power at given RPM.
Real Estate19
Decision-support calculators for buyers, sellers, and small landlords.
Cap Rate Calculator
Capitalization rate = NOI / Property Value × 100. Property's annual return excluding financing.
Cash-on-Cash Return Calculator
Annual pre-tax cash flow / total cash invested × 100. Measures return on actual money in.
NOI (Net Operating Income) Calculator
NOI = gross income − operating expenses. Excludes mortgage payments, capex, depreciation, and income tax.
Gross Rent Multiplier (GRM) Calculator
GRM = property price / gross annual rent. Quick screening metric (lower is better).
DSCR (Debt Service Coverage Ratio) Calculator
DSCR = NOI / annual debt service. Lenders typically require ≥ 1.20-1.25.
Rental Property ROI Calculator
Total return = (cash flow + appreciation + principal pay-down + tax benefit) / cash invested. The full picture.
1% Rule Calculator
Quick rental screening: monthly rent should be ≥ 1% of purchase price.
50% Rule Calculator
Rule of thumb: operating expenses ≈ 50% of gross rent. Quick NOI estimator.
BRRRR Method Calculator
Buy + Rehab → Rent → Refinance (75% LTV) → Repeat. Compute cash recovered + ongoing cash flow.
Fix-and-Flip Profit Calculator
Profit = sale − purchase − rehab − holding − selling costs.
Property Holding Cost Calculator
Holding = (taxes + insurance + utilities + interest) × months.
Rehab Budget Calculator
Sum cosmetic / mid / heavy rehab line items + contingency.
After-Repair Value (ARV) Calculator
ARV = avg comp $/ft² × subject ft². Average from 3-5 sold comps within 1 mile, last 6 months.
Max Purchase Price (Target Cap Rate)
Max purchase = NOI / target cap rate. Reverse-engineer from desired return.
Cash-Out Refinance Calculator
Cash out = (new loan − old loan payoff) − closing costs.
1031 Exchange Basis Calculator
New basis = old adjusted basis + boot − deferred gain. Section 1031 like-kind tax deferral.
Buy vs Rent Breakeven Years
Years until total ownership cost (mortgage + property tax + maintenance + opportunity) equals total rent.
Mortgage Points Break-Even Calculator
Decide whether paying discount points is worth it: compare monthly payments with and without points and find the break-even month.
Mortgage PMI Removal Calculator
Find when your private mortgage insurance can be removed — the month your loan reaches 80% LTV (request) and 78% LTV (automatic termination).
Education17
Grading, GPA, and test-score calculators for students and educators.
College GPA Calculator
Compute GPA on the standard 4.0 scale from a list of courses (grade, credits).
High School GPA Calculator (unweighted)
Compute unweighted high-school GPA on a 4.0 scale.
Weighted GPA Calculator
Bonus points for AP/IB (+1.0) or honors (+0.5) courses on a 5.0-max scale.
Semester GPA Target Calculator
What GPA do you need this semester to reach a desired cumulative GPA?
Course Grade Needed Calculator
Given current grade and weight remaining, what do you need on the rest to hit a target?
Final Grade Calculator
Compute your final letter grade from a list of weighted assignment scores.
Exam Grade Required
Score needed on final exam to hit course target. (Target − pre-exam × pre-weight) / exam-weight.
Cumulative GPA After Semester
New cumulative GPA = (current cum × completed credits + semester GPA × new credits) / total.
Semester Credits Required
Total degree credits / semesters remaining = credits per semester.
Study Hours Per Credit (Weekly Load)
Weekly study load = credits × hours per credit. Standard 2-3 hr study per credit hour.
College Tuition Cost Projection
Tuition × (1 + inflation)^years. Plan ahead; tuition has historically risen 5-7%/yr.
Student Loan: Standard vs PSLF
Compare 10-year standard payoff vs. 10-year IDR + PSLF forgiveness for federal loans.
Student Loan Monthly Payment
Standard 10-year amortization payment for federal/private loans.
Total Cost of Degree
Tuition + fees + room/board + books + opportunity cost over years.
FAFSA SAI / EFC Estimator
Simplified FAFSA Student Aid Index (formerly EFC) estimate.
529 Plan Growth Projection
Tax-advantaged 529 college savings: monthly contribution + growth over years.
Scholarship Application ROI
Hours spent applying / expected $ won. Compare to part-time wage.
Insurance19
Coverage-needs and cost calculators for life, auto, home, health, disability, and long-term-care insurance.
Life Insurance Needs Calculator (DIME)
How much life insurance do you need? DIME = Debt + Income (× years) + Mortgage + Education.
Term vs Whole Life Comparison
Compare 30-year cost: cheap term + invest-the-difference vs more-expensive whole life with cash value.
Auto Insurance Rate Estimator
Rough estimate based on US-average factors: age, credit, territory, driving history.
Home Insurance Replacement Cost Estimator
Replacement cost = sq ft × $/ft² for your construction class. (Different from market value!)
Umbrella Policy Coverage Calculator
Recommended umbrella coverage = net worth + 5-10× annual income (lawsuit-protection rule of thumb).
Disability Insurance Needs Calculator
Compute monthly benefit needed: typically 60-70% of gross income, less Social Security DI.
Long-Term Care Insurance Cost Estimator
Average annual premium varies sharply with age at issue — buying earlier is much cheaper.
Annuity Payout Calculator
Fixed monthly payout from annuity principal: PMT = P × r / (1 − (1+r)^(−n)).
Health Plan: Deductible vs Premium
Total annual cost = premiums × 12 + expected medical × cost-share until OOPM.
HSA Tax Savings Calculator
Tax saved = contribution × marginal tax bracket. Triple tax advantage with HDHP.
FSA Tax Savings Calculator
Tax saved = contribution × marginal rate. Use-it-or-lose-it (with $640 max carryover 2025).
Life Insurance Cash Surrender Value
Cash surrender = cash value − surrender charges. Estimate before cancelling permanent policy.
Insurance Bundling Savings
Auto + Home from same carrier typically saves 5-25%.
COBRA vs ACA Marketplace Cost
COBRA = full premium + 2% admin. Marketplace = unsubsidized premium with possible subsidy.
ACA Subsidy Estimator
Premium tax credit caps benchmark Silver plan at 0-8.5% of income (sliding scale).
Home Replacement Cost
Replacement cost = sq ft × $/ft² (region + quality). Different from market value.
Homeowners Deductible Tradeoff
Annual savings × years until deductible jump pays back.
Auto Liability Coverage Minimums
State minimums shown vs recommended; coverage shortfall risk.
Pet Insurance ROI vs Out-of-Pocket
Premium total vs expected vet costs over pet lifetime.
Business Finance67
Time-value-of-money and financial-statement-analysis calculators. Distinct from the consumer-/finance/ cluster of mortgages and loans.
Present Value Calculator
PV = FV / (1 + r)^n. The current worth of a future cash flow.
Future Value Calculator
FV = PV × (1 + r)^n. What today's amount grows to over time.
Annuity Payment Calculator
PMT = P · r / (1 − (1+r)^(−n)). Payment that fully amortizes a principal over n periods at rate r.
Perpetuity Value Calculator
V = C / r — present value of an infinite stream of equal cash flows.
NPV (Net Present Value) Calculator
NPV = sum of discounted future cash flows minus initial investment. Positive NPV = accept project.
IRR (Internal Rate of Return) Calculator
IRR = the discount rate that makes NPV = 0. Solved numerically via Newton's method.
Payback Period Calculator
How many years until cumulative cash flows equal the initial investment.
Discounted Payback Period Calculator
Years for discounted cash flows to recoup initial investment. Time-value-aware variant of payback.
MIRR (Modified IRR) Calculator
IRR with explicit reinvestment-rate assumption. Avoids the multiple-IRR problem.
Profitability Index Calculator
PI = (NPV + initial) / initial = PV of future flows / initial investment. >1 = accept.
Discount Calculator
Sale price and savings from a percent-off, dollar-off, or stacked-coupon discount.
Tip Percentage Finder
Reverse-tip calculator: enter the bill and the tip you left, get the implied tip %.
Bond Yield Calculator
Current yield and yield-to-maturity (YTM) for a fixed-coupon bond, solved numerically via Newton-Raphson.
Tip & Bill Split Calculator
Calculate tip, split the bill among any number of people with per-person subtotal/tip/total, and optionally round each share up to the next dollar.
Compound Interest Calculator (with Monthly Contributions)
See how an initial deposit + steady monthly contributions grow over time with compound interest.
WACC Calculator
WACC = (E/V)·Re + (D/V)·Rd·(1−T). Blended cost of capital weighted by debt + equity.
Dividend Discount Model (DDM)
P = D₁ / (r − g). Stock price = next dividend / (required return − growth rate).
Gordon Growth Model
Same as DDM: P = D₁ / (k − g). Single-stage constant-growth model.
Free Cash Flow (FCF)
FCF = EBIT(1−T) + D&A − CapEx − ΔNWC. Cash available to all capital providers.
EBITDA Calculator
EBITDA = Net Income + Interest + Tax + D&A. Operating earnings before financing + non-cash items.
Current Ratio
Current ratio = Current Assets / Current Liabilities. Liquidity benchmark.
Quick Ratio (Acid Test)
(Current assets − Inventory) / Current liabilities. Stricter than current ratio.
Debt-to-Equity Ratio
D/E = Total Debt / Total Equity. Leverage relative to ownership.
Return on Equity (ROE)
ROE = Net Income / Avg Shareholders' Equity. Profitability per dollar of equity.
Health & Clinical19
Clinically validated calculators with formulas cited to original journals (NEJM, JAMA, Circulation, etc.). Educational reference; not medical advice.
A1c to eAG (Estimated Average Glucose) Calculator
Convert HbA1c (%) to estimated average glucose: eAG (mg/dL) = 28.7 × A1c − 46.7. ADAG / Nathan 2008.
eAG (Average Glucose) to A1c Calculator
Convert estimated average glucose back to HbA1c: A1c (%) = (eAG + 46.7) / 28.7. ADAG / Nathan 2008 inverse.
eGFR (CKD-EPI 2021, race-free) Calculator
eGFR from creatinine, age, sex per CKD-EPI 2021 (Inker et al., NEJM). Race-free formula adopted by NKF/ASN.
LDL Cholesterol (Friedewald) Calculator
LDL = TC − HDL − TG/5 (mg/dL). Friedewald 1972 Clin Chem. Not valid if triglycerides > 400 mg/dL.
MELD-Na Score Calculator (Liver Allocation)
MELD-Na = MELD + 1.32 × (137 − Na) − [0.033 × MELD × (137 − Na)]. UNOS 2016 update; Kim 2008 NEJM.
CHA₂DS₂-VASc Score Calculator (Stroke Risk in AF)
Stroke-risk score in non-valvular atrial fibrillation. Lip 2010 Chest. ESC/AHA recommend OAC if score ≥2 (men) / ≥3 (women).
Wells Score Calculator (Pulmonary Embolism)
Wells PE score — pretest probability for pulmonary embolism. Wells 2000 Annals Intern Med (modified).
CURB-65 Calculator (Pneumonia Severity)
CURB-65 = Confusion + Urea>7 + RR≥30 + BP<90/60 + Age≥65. Lim 2003 Thorax. Predicts 30-day pneumonia mortality.
Framingham 10-Year CVD Risk Calculator
10-year general cardiovascular disease risk per D'Agostino 2008 Circulation. Sex-specific, lab-based.
FRAX-Style Fracture Risk Estimator (Educational)
Approximate 10-year major osteoporotic & hip fracture risk from age, sex, BMD T-score, and clinical risk factors. Educational only — for clinical use, see frax.shef.ac.uk/FRAX.
Bra Size Calculator
Compute US bra size from band and bust measurements, with US ↔ UK ↔ EU conversion table.
Pregnancy Weight Gain Calculator
Recommended weight-gain range during pregnancy by pre-pregnancy BMI category — Institute of Medicine 2009 guidelines.
Body Water Percentage Calculator (Watson formula)
Total body water in litres and as % of body mass, via the Watson (1980) anthropometric formula. Illustrative — consult a professional for clinical use.
Glycemic Load Calculator
GL = (GI × available carbs in serving) ÷ 100 — total daily glycemic load for up to 6 foods. Harvard / Sydney University GI database values.
Cardio Target Distance for Weekly Volume
Plan weekly running/cycling/swimming mileage from target weekly time × pace. 10% rule progression alerts + ACSM guideline check.
Calorie Deficit to Weight Loss Timeline
Estimate how long it takes to lose a target amount of weight from a given daily calorie deficit, using the 3,500-calories-per-pound rule.
Macro Calculator (Cut, Maintain, Bulk)
Turn your TDEE and goal into daily calorie targets and protein, carb, and fat grams using a goal-appropriate macronutrient split.
Pregnancy Week Estimator (LMP-based)
Estimate gestational age and due date from the first day of your last menstrual period (LMP), using Naegele’s rule.
Water Bottle Intake Calculator
Convert a daily water target in ounces or litres into how many bottles you need across common bottle sizes.
Misc51
Cross-cutting calculators that don't fit the existing categories — personal finance specials, business analytics, life decisions.
Tip Split Calculator
Compute tip and split a restaurant bill evenly among diners.
Fuel vs Electric Car Cost Comparison
Annual fuel cost (gas car) vs annual electricity cost (EV) for the same mileage.
EV Charging Cost Calculator
Cost per session: kWh delivered × $/kWh, accounting for charger efficiency.
Solar Panel Payback Period
System cost / annual savings = years to break even on a residential solar install.
Mortgage vs Renting (Detailed)
30-year comparison: ownership equity + appreciation vs rent + alternative-investment growth.
College Degree ROI Calculator
Lifetime income premium vs total cost (tuition + 4 years of foregone earnings).
Hourly Rate from Target Income
Target salary / billable hours = required hourly rate.
Freelance Rate Pricing Calculator
(Target salary + overhead + profit margin) / billable hours = full freelance hourly rate.
CAC vs LTV Ratio
LTV / CAC ratio. Healthy SaaS: 3:1+; under 1:1 burns money.
Conversion Rate Needed for Target Revenue
Conv % = target revenue / (visitors × avg order value).
Email List Campaign ROI
Sends × open rate × CTR × conv × AOV → revenue. Compare to send cost.
Podcast CPM Revenue
Revenue = (downloads / 1000) × CPM × ad slots.
Video Render Time Estimator
Render time = (duration × frames/sec × complexity) / machine speed.
Cloud Storage Cost Comparison
Compare AWS S3 / B2 / R2 / Glacier monthly + retrieval costs.
Subscription Cancellation ROI
Recouped = monthly savings × months you keep it cancelled.
Hex / Binary / Octal / Decimal Converter
Convert numbers between hexadecimal, binary, octal, and decimal. Shows the bit pattern grouped by nibble + the two’s-complement representation for negative values.
ASCII / Unicode Codepoint Lookup
Look up the ASCII/Unicode codepoint for any character — or go the other way and turn a list of codepoints back into text. Shows decimal, hex (U+XXXX), octal, binary, HTML entity, JS escape, and URL-encoded forms for every code point.
Word Count + Reading Time
Count words, characters, paragraphs, and sentences in any pasted text, plus reading time at 250 / 200 / 150 WPM.
Lorem Ipsum Generator
Generate placeholder text — paragraphs, sentences, or words — in deterministic seeded form. Starts with the classic "Lorem ipsum dolor sit amet" opening.
Password Strength Tester (Entropy Bits)
Estimate password entropy in bits and the time an offline brute-force attacker would need at common cracking rates. Pure client-side — your password is never sent anywhere.
Random Password Generator
Generate strong, deterministically-seeded passwords. Pick length, character classes, and bulk-count. All client-side — passwords never leave the browser.
QR Code Payload Formatter (text / URL / WiFi / vCard)
Build the canonical text payload encoded in a QR code — plain text, URL, WiFi-network credentials, or vCard contact. Includes a ready-to-render image URL for visual scanning.
Barcode Validator (EAN-13 / UPC-A / Code 128)
Validate a barcode number, compute the check digit, and produce a ready-to-render image URL. Supports EAN-13, EAN-8, UPC-A, Code 128, and ISBN.
Color Picker (hex / rgb / hsl / hwb)
Convert a color between hex, RGB, HSL, HWB, and CMYK. Reports relative luminance and WCAG 2.2 contrast ratio against white and black.