Rectangle Calculator
Enter the width and height to calculate a rectangle's area, perimeter, and diagonal length. Handy for math problems and interior design — all calculations happen inside your browser.
Enter the width and height to see the result.
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Area
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Perimeter
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Diagonal
How to use
- Enter the width.
- Enter the height.
- The area, perimeter, and diagonal length are shown in real time.
Frequently asked questions
How do I find the area of a rectangle?
The area of a rectangle is the width times the height: area = width × height.
How do I find the diagonal length?
The diagonal is found with the Pythagorean theorem: diagonal = √(width² + height²).
Are the values I enter sent to a server?
No. All calculations happen only inside your browser, and the values you enter are never sent to or stored on any server.