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Rectangle Calculator

Use our free rectangle calculator to find the area, perimeter, and diagonal of any rectangle. Enter the width and height and get all measurements instantly.

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Width (w)

Height (h)

Formula

A rectangle is a quadrilateral with four right angles. Opposite sides are equal and parallel. This calculator computes the area (A = w × h), perimeter (P = 2(w + h)), and diagonal (d = √(w² + h²)).

A = w × h, P = 2(w + h)

Percentage: The percentage value you want to apply

Number: The original number or value

Result: The calculated result

How It Works

1Enter the width of the rectangle.
2Enter the height of the rectangle.
3Click Calculate to see area and perimeter.
4Area = width × height.
5Perimeter = 2 × (width + height).

Examples

Rectangle with width 8 and height 5

1.Enter width = 8, height = 5.
2.Area = 8 × 5 = 40 units².
3.Perimeter = 2 × (8 + 5) = 26 units.

Result: Area: 40.0000, Perimeter: 26.0000

Rectangle with width 12 and height 3

1.Enter width = 12, height = 3.
2.Area = 12 × 3 = 36 units².
3.Perimeter = 2 × (12 + 3) = 30 units.

Result: Area: 36.0000, Perimeter: 30.0000

Frequently Asked Questions

Area = width × height. For example, a rectangle 8 units wide and 5 units tall has an area of 40 square units.

Perimeter = 2 × (width + height). For an 8 by 5 rectangle, the perimeter is 2 × (8 + 5) = 26 units.

The diagonal can be found using the Pythagorean theorem: d = √(w² + h²). The diagonal of an 8 by 5 rectangle is √(64 + 25) = √89 ≈ 9.434 units.

A square is a special rectangle where all four sides are equal. Every square is a rectangle, but not every rectangle is a square.

Yes. The terms width and height are just labels. The calculator works regardless of which dimension is larger.

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CalculateMe Team

Last updated: 2026-07-13

Rectangle Calculator - Area, Perimeter, Diagonal | CalculateMe | CalculateMe