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Rectangle Area & Perimeter Calculator

Area, perimeter, and diagonal of a rectangle.

Compute the area, perimeter, and diagonal of a rectangle from its length and width.

Daniel Oh By Daniel Oh
Published Last reviewed 1 min read

Inputs

Results

Enter values and click Calculate to see results.
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How to use this calculator

  1. Fill in the inputs above using the units you already have.
  2. Values update automatically as you type — no submit button needed.
  3. Hover any result row for the underlying formula and intermediate values.

Formula

Area = L × W, Perimeter = 2(L + W), Diagonal = √(L² + W²).

In depth

Compute the area, perimeter, and diagonal of a rectangle from its length and width.