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Math

Rectangle Calculator

Find a rectangle’s area, perimeter and diagonal from length and width.

Exact method explained belowEditable inputs

Set up your calculation

Runs on your device

SOLUTION

Your result

Let’s calculate.

Use the Calculate button to see your result.

Review the method below for assumptions and conventions.

How to use this tool

  1. Enter length, width.
  2. Select Calculate to view the result.
  3. Check the method and assumptions below before using the result.

The method, explained

Area = length × width. Perimeter = 2(length + width). Diagonal = √(length² + width²).

A WORKED EXAMPLE

An 8 by 6 rectangle has area 48, perimeter 28 and diagonal 10.

What to keep in mind

Both dimensions use the same length unit. The formula assumes four right angles; it does not describe an arbitrary quadrilateral.

Common questions

What units are used for area?

The length unit squared. Meter inputs produce square meters.

Can this calculate a square?

Yes. Use equal length and width.

Methodology maintained by ClarityKit. How these tools are built and checked.