Geometry & Measurement Calculators
Rectangle Calculator
Calculate the area, perimeter and diagonal of a rectangle.
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What is Rectangle?
A rectangle has four right angles. Its area is length × width, and its diagonal follows from the Pythagorean theorem.
How it works
We multiply for area, double the sum for perimeter, and apply √(l² + w²) for the diagonal.
- Enter your input. Type or paste your input into the field above — the tool responds instantly.
- Review the result. Output updates live as you type. Everything runs entirely in your browser.
- Copy or download. Use the Copy button to grab the result, or Download to save it as a file.
Examples
Realistic sample
Type or paste any realistic input — the tool computes the result locally and instantly.
Common mistakes
Expecting a server round-trip
Nothing is uploaded — every tool in this category runs entirely in your browser.