What is the Rectangle Calculator?
Calculate the area, perimeter and diagonal of a rectangle.
Enter length and width and the Rectangle Calculator returns area, perimeter and diagonal. Results update as you type, and nothing you enter leaves your device.
How it is calculated
Area = length × width
Perimeter = 2 × (length + width)
How to use it
- Enter length.
- Enter width.
- Read area in the results panel. It updates as you type.
- Change any value to compare scenarios, or use Share to send the result as a link.
Worked example
Common questions
What formula does the Rectangle Calculator use?
It uses: Area = length × width; Perimeter = 2 × (length + width).
What do I need to use the Rectangle Calculator?
You need length and width. Sensible starting values are filled in so you can see how it works straight away.
Is the Rectangle Calculator free, and is my data stored?
It is free with no sign-up. The calculation runs in your browser, so the values you enter are not sent to or stored on our server.