Perimeter Calculator

Perimeter of squares, rectangles, triangles and regular polygons, plus circumference.

Perimeter Calculator

Worked example result

Perimeter	43.9823
Shape calculated	circle

A circle with radius 7 has a circumference of 2 × π × 7 ≈ 43.98 — the distance a wheel of that size rolls in one full turn.

The perimeter is the total distance around the outside of a shape — the length of fence, trim or edging you would need to surround it. For a circle, the same measurement is called the circumference.

Choose a shape and enter its dimensions: A is the side (square), length or first side (rectangle and triangle) or radius (circle); for a triangle, B and C are the other two sides; for a regular polygon, A is one side's length and you also set how many sides it has.

The formula

Square 4a · Rectangle 2(a+b) · Circle 2πr · Triangle a+b+c · Regular polygon n × side

Worked example

A circle with radius 7 has a circumference of 2 × π × 7 ≈ 43.98 — the distance a wheel of that size rolls in one full turn.

The example is pre-loaded in the result panel — press Calculate with your own numbers to replace it.

Frequently asked questions

What is the difference between perimeter and circumference?

None in concept — circumference is simply the name for the perimeter of a circle. Both measure the distance once around the shape.

What is a regular polygon?

A polygon with all sides and angles equal: an equilateral triangle (3 sides), a square (4), a regular pentagon (5), hexagon (6) and so on. Its perimeter is just the side count times one side's length.

Category: Math calculators

Perimeter Calculator