Perimeter Calculator
Perimeter of squares, rectangles, triangles and regular polygons, plus circumference.
Quick answer
- Formula: Square 4a · Rectangle 2(a+b) · Circle 2πr · Triangle a+b+c · Regular polygon n × side
- Worked example — Perimeter: 43.9823 (full example below).
Perimeter Calculator
| 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
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
Sources & methodology
This calculator applies the formula shown on this page exactly as written, using the standard definitions for its inputs. Results are computed from the values you enter — no data is stored — and are rounded only for display.
Content last reviewed by CalcHub Editorial.
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