Perimeter Calculator for Any Shape, with Steps
Choose a shape and enter its sides. You get the perimeter (or circumference), the area where it can be worked out, and the steps.
- Nothing you type is stored
- Free
- No signup
Perimeter
40m
- Area
- 96 m²
- Perimeter in metres
- 40 m
Show working
- P = 2 × (l + b)
- P = 2 × (12 + 8) = 40 m
How to use
- Choose the shape.
- Enter the side lengths (or radius) and pick a unit.
- Read the perimeter and the working below it.
Good to know
Perimeter is the total length of the boundary: add all the sides. For a rectangle P = 2(l + b), a square 4a, a circle 2πr (called the circumference), and a sector 2r + arc length.
For a triangle the calculator also checks that the sides can form a triangle (any two sides must add up to more than the third) and finds the area with Heron's formula from NCERT Class 9.
An ellipse has no exact school formula for its perimeter, so this uses Ramanujan's approximation, which is very close for everyday shapes. Fencing, borders, lace and skirting are typical real uses: buy a little extra for joints and waste.
Questions
What is the difference between perimeter and area?
Perimeter is the length around a shape (in m, cm). Area is the space inside it (in m², cm²).
What is the perimeter of a circle called?
Circumference. C = 2πr or πd.
How do I find the perimeter of a rhombus?
All four sides are equal, so P = 4 × side. If you know only the diagonals, side = √((d₁/2)² + (d₂/2)²).
How much fencing do I need for a rectangular plot?
Enter the plot length and breadth as a rectangle; the perimeter is the fence length. Subtract gate width if needed.
Is anything I enter stored?
No. The calculation runs in your browser and nothing is sent to a server.