Perimeter Calculator
Pick a shape below to instantly get its perimeter.
Perimeter
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Perimeter Formulas by Shape
- Rectangle: 2(l + w)
- Square: 4s
- Triangle: a + b + c
- Circle (circumference): 2πr
- Regular polygon: number of sides × side length
Working with a regular hexagon or a trapezoid specifically? See the dedicated hexagon or trapezoid calculators.
Frequently Asked Questions
What is perimeter?
Perimeter is the total distance around the outside edge of a two-dimensional shape — add up the length of every side.
What's the difference between perimeter and circumference?
They're the same idea — the distance around a shape's outer edge — but "circumference" is the specific term used only for circles.
How do you find the perimeter of an irregular shape?
Add up the length of every individual side, even if they're all different lengths. The formulas here are shortcuts for shapes where the sides follow a predictable pattern (all equal, or opposite sides equal).
Related Calculators
- Sphere Calculator — Geometry & Trigonometry
- Cylinder Calculator — Geometry & Trigonometry
- Cone Calculator — Geometry & Trigonometry
- Triangle Area Calculator — Geometry & Trigonometry