Perimeter Calculator
Find the perimeter of common shapes. You also get the area and the formula with your numbers.
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Units
- Area
- Area formula
- Work
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| Name | Calculation | Result | Remove |
|---|
Perimeter and Area Formulas
Pick a shape and enter its measurements in any one unit (inches, feet, meters). Perimeter comes out in the same unit.
| Shape | Area | Perimeter |
|---|---|---|
| Square | a² | 4a |
| Rectangle | l × w | 2(l + w) |
| Triangle | ½ × b × h, or Heron √(s(s−a)(s−b)(s−c)) | a + b + c |
| Circle | πr² | 2πr |
| Ellipse | πab | ≈ π(a + b)(1 + 3h/(10 + √(4 − 3h))), h = ((a − b)/(a + b))² |
| Trapezoid | (a + b)/2 × h | a + b + both legs |
| Parallelogram | b × h | 2(b + s) |
| Rhombus | p × q ÷ 2 | 4 × √((p/2)² + (q/2)²) |
| Regular polygon | n s² ÷ (4 tan(180°/n)) | n × s |
| Sector | πr² × θ/360 | 2r + 2πr × θ/360 |
| Ring | π(R² − r²) | 2π(R + r) |
Worked Example
Tips
An ellipse has no simple exact perimeter formula; Ramanujan’s approximation is accurate to far better than 0.01% for everyday shapes. For a room or lot made of several rectangles, split it up and add the areas. For the triangle, the three sides must satisfy the triangle inequality.