Math

Rectangle Calculator

Enter the length and width to find the area, perimeter and diagonal.

By TheCalcTools Updated Formula checked and tested

Your numbers

Your results

Area
Area
—
Perimeter
—
Diagonal
—

Rectangle Calculator by TheCalcTools

How the Rectangle Calculator works

Enter both sides in the same unit.

Area is length times width; perimeter is twice the sum of the sides.

The diagonal uses the Pythagorean theorem.

The formula

A = l × wP = 2(l + w)

Worked example

Using the default values shown in the calculator:

Length12
Width5
  1. Area = 12 × 5 = 60.
  2. Perimeter = 2 × (12 + 5) = 34.
  3. Diagonal = √(144 + 25) = 13.00.

Result:

Area60.00
Perimeter34.00
Diagonal13.0000

Frequently asked questions

Is a square a rectangle?

Yes. A square is a rectangle whose length equals its width.

How do I find a side from the area?

Divide the area by the other side.

Sources and further reading

Trapezoid Area CalculatorEnter the two parallel sides and the height to find the area of a trapezoid Circle CalculatorEnter the radius to get the diameter, circumference and area of a circle Triangle Calculator (Solve Any Triangle: SSS, SAS, ASA)Choose what you know and enter the values Triangle Area Calculator (Heron's Formula)Enter three side lengths to find the triangle's area, perimeter and angles Pythagorean Theorem CalculatorSolve for any side of a right triangle using a² + b² = c² Sphere Volume and Surface Area CalculatorEnter the radius to find the volume and surface area of a sphere

More in Math · All calculators

This calculator gives estimates for information only. Check important results independently before you rely on them. See our disclaimer.