Perimeter Calculator – Rectangle, Square and Circle
Find the boundary length of a rectangle, square or circle from its dimensions.
Formula
Rectangle: 2(a+b); square: 4a; circle: 2πa (a is radius).
Length / side / radius a: 6 cm · Rectangle width b: 4 cm · Perimeter ≈ 2×((6 cm × 0.01 m/cm)+(4 cm × 0.01 m/cm))×100
How to use
- Choose the shape.
- Enter its dimensions and units.
- Read the perimeter in cm.
Examples
- A 6 cm × 4 cm rectangle has perimeter 20 cm.
Frequently asked questions
Which measurements are needed?
Rectangle: length a and width b. Square: side a. Circle: radius a.
What happens to unused b?
Keep any positive value; b is used only for rectangles.
Is perimeter an area?
No. Perimeter is boundary length; area measures the enclosed surface.
Sources
Updated: