Area of a Rectangle Calculator
A = length × width.
Result
Area
40.0000 units²
Perimeter: 26.0000, diagonal: 9.4340.
- Length8
- Width5
- Perimeter26.0000
- Diagonal9.4340
- Aspect ratio1.600 : 1
Step-by-step
- Area = l × w = 8 × 5 = 40.0000.
- Diagonal (Pythagoras): √(8² + 5²) = 9.4340.
How to use this calculator
- Enter length and width in any unit.
- Read area, perimeter, and diagonal.
About this calculator
The most basic formula in geometry: length × width. The diagonal is computed via the Pythagorean theorem. This formula extends to any 2D space — a rectangle on a map, a wall to be painted, a piece of fabric.
Frequently asked
No — multiplication is commutative.
Related calculators
Area of a Square Calculator
A = s² where s is the side length.
Area of a Parallelogram Calculator
A = base × height (perpendicular height).
Area of a Trapezoid Calculator
A = ½ × (parallel side a + parallel side b) × height.
Area of a Circle Calculator
Calculate the area of a circle given its radius (or diameter). A = πr².
Area of a Triangle Calculator
Three formulas: base × height ÷ 2, SAS (two sides and angle), and Heron's (three sides).
Area of a Rhombus Calculator
A = (d₁ × d₂) / 2 — half the product of the diagonals.