About the Rectangle Calculator
Area, perimeter and diagonal of a rectangle from its length and width, with the aspect ratio.
Also known as: rectangle area, area of rectangle, rectangle perimeter, length times width, rectangle area calculator.
How to use this calculator
- Enter length, width.
- The result updates instantly as you type — press Calculate (or Enter) at any time.
- Review the breakdown shown under the main result.
- Use Copy result or Share to save the answer or send a link with your inputs.
Formula
A = l × w · P = 2(l + w) · d = √(l² + w²)
Worked example
Using the values pre-filled in the calculator above:
- Length = 12
- Width = 8
the calculator returns:
- Area: 96
- Perimeter: 40
- Diagonal: 14.422205