Result
- Sedentary TDEE (×1.2)desk job, minimal walking2,061 kcal/day
- Lightly active TDEE (×1.375)1-3 days/wk light exercise2,362 kcal/day
- Moderately active TDEE (×1.55)3-5 days/wk moderate exercise2,662 kcal/day
- Very active TDEE (×1.725)6-7 days/wk hard exercise2,963 kcal/day
- Extra active TDEE (×1.9)athlete or physical job3,263 kcal/day
How to use this calculator
- Pick a formula. Mifflin-St Jeor is the default and the most accurate for most adults.
- Enter sex, age, weight, and height. Choose Katch-McArdle only if you have a measured body fat % (DEXA, BodPod, or a calibrated bioimpedance scale).
- Read the BMR figure — that is your rest-only calorie need. The TDEE rows below show what you would need at various activity levels.
About this tool
Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest to keep its core processes running — heart, lungs, brain, body temperature, and cell maintenance. It accounts for roughly 60–75% of your total daily energy expenditure for a typical sedentary adult. BMR is not the same as TDEE (Total Daily Energy Expenditure): TDEE = BMR × an activity factor that adds movement, digestion, and exercise. Use BMR when you want the rest-only baseline; use TDEE when planning a calorie target for weight maintenance or change. The Mifflin-St Jeor equation (used here as the default) is the most accurate published BMR predictor for healthy non-obese adults, tracking measured resting energy expenditure within roughly 5% in validation studies.
What this calculator does
Estimates your Basal Metabolic Rate — the calories your body burns at complete rest — using the formula you select. Mifflin-St Jeor is recommended for most adults; Harris-Benedict (revised) is shown for comparison and historical reference ranges; Katch-McArdle uses lean body mass when you have a measured body fat percentage.
How it works — the formula
Mifflin-St Jeor (1990):
Men: 10·W(kg) + 6.25·H(cm) − 5·A(yr) + 5
Women: 10·W(kg) + 6.25·H(cm) − 5·A(yr) − 161
Harris-Benedict (Roza-Shizgal 1984 revision):
Men: 88.362 + 13.397·W + 4.799·H − 5.677·A
Women: 447.593 + 9.247·W + 3.098·H − 4.330·A
Katch-McArdle:
BMR = 370 + 21.6 · LBM(kg), where LBM = W · (1 − BF%/100)All three formulas predict resting energy expenditure in kcal/day. Mifflin-St Jeor is the modern default — derived on a broader, heavier sample than Harris-Benedict and validated to within ±5% in over half of healthy adults. The Harris-Benedict revision adjusts the 1919 original to fit late-20th-century population norms but still tends to over-predict BMR by 3-5%. Katch-McArdle replaces the height/sex/age proxies with direct lean-body-mass and is preferred when an accurate body fat % is available (DEXA or similar).
Worked examples
- Inputs:
- formula = Mifflin-St Jeor, sex = male, age = 30, weight = 75 kg, height = 178 cm
- Output:
- 10·75 + 6.25·178 − 5·30 + 5 = 750 + 1,112.5 − 150 + 5 ≈ 1,718 kcal/day
Multiply by 1.55 for a moderately active TDEE ≈ 2,663 kcal/day.
- Inputs:
- formula = Mifflin-St Jeor, sex = female, age = 40, weight = 65 kg, height = 165 cm
- Output:
- 10·65 + 6.25·165 − 5·40 − 161 = 650 + 1,031.25 − 200 − 161 ≈ 1,320 kcal/day
Sedentary TDEE ≈ 1,320 × 1.2 = 1,584 kcal/day; a 500-kcal deficit puts maintenance below 1,100 — too low. Add walking instead of cutting further.
- Inputs:
- formula = Katch-McArdle, weight = 80 kg, body fat = 15%
- Output:
- LBM = 80 · 0.85 = 68 kg; BMR = 370 + 21.6·68 ≈ 1,839 kcal/day
For an athlete training 6 days/week, multiply by 1.725 → TDEE ≈ 3,172 kcal/day.
When to use this vs other tools
BMR is the rest-only baseline. If you actually want a daily calorie target, pick TDEE or one of the goal-aware tools below.
- Calorie Calculator (TDEE)
You want a daily calorie target that accounts for activity — TDEE = BMR × activity factor.
- Macro Calculator
You already know your calorie target and need to split it into protein, carbs, and fat.
- Protein Calculator
You only need a daily protein target by body weight and training goal.
- Lean Body Mass Calculator
You need an estimate of LBM to feed into the Katch-McArdle formula or to track body recomposition.
Authority note
Mifflin-St Jeor remains the formula endorsed by the Academy of Nutrition and Dietetics evidence-analysis review (Frankenfield 2005) as most accurate for healthy non-obese adults; the calculator defaults to it for that reason.
Limitations
- BMR equations were calibrated on healthy adults aged ~19–78. Pregnancy, lactation, hyperthyroidism, hypothyroidism, fever, and post-surgical states all shift true resting expenditure outside the predicted range.
- Predictions degrade in extremes of body composition. In adults with BMI > 40, Mifflin-St Jeor tends to over-predict; in very lean athletes, Katch-McArdle is the better choice if a real body fat measurement is available.
- BMR is not RMR. Resting Metabolic Rate (RMR) is measured under less strict conditions than BMR and runs about 10% higher; most modern equations (Mifflin-St Jeor included) are technically RMR predictors despite the BMR label.
- These equations cannot detect adaptive thermogenesis after sustained dieting, which can suppress real BMR 5–15% below the predicted figure for months after weight loss.
For general planning and educational use only. This calculator does not provide medical, nutrition, or weight-management advice. Consult a registered dietitian or physician before basing a clinical intervention on these numbers.