Free Perimeter Calculator — Squares, Rectangles, Circles & Triangles

Calculate the perimeter or circumference of any shape by entering its dimensions.

Perimeter Calculator

Shape

Perimeter

How to Use

Select your shape from the dropdown — the input fields update automatically to match. Enter the required dimensions in any unit (cm, m, inches — the result uses the same unit). Click Calculate to see the perimeter. For a circle, the result is the circumference (2πr).

Worked Examples

Square

Side5 m

P = 4 × 5 = 20 m

Rectangle

Width8 m

Height4 m

P = 2(8+4) = 24 m

Circle

Radius7 m

C = 2π×7 ≈ 43.98 m

Frequently Asked Questions

Perimeter is the total length of the boundary of a 2D shape — the distance you would walk if you walked around its edge. It is measured in linear units (m, cm, ft, in).

P = 2 × (width + height). For a rectangle 8m wide and 4m tall: P = 2 × (8+4) = 24m.

Circumference is the perimeter of a circle. Formula: C = 2πr = πd, where r is the radius and d is the diameter. For a circle with radius 5m: C = 2 × 3.14159 × 5 ≈ 31.42m.

Add the three side lengths together. For a triangle with sides 3, 4 and 5: P = 3+4+5 = 12 units.

Free Perimeter Calculator — Squares, Rectangles, Circles & Triangles

Perimeter Calculator

How to Use

Worked Examples

Frequently Asked Questions

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