How it is calculated
| Shape | Area | Perimeter |
|---|---|---|
| Square | a² | 4a |
| Rectangle | a × b | 2(a + b) |
| Triangle | ½ × base × height | a + b + c |
| Circle | π r² | 2 π r |
| Trapezoid | ½ (a + b) × h | sum of sides |
| Parallelogram | base × height | 2(a + b) |
| Rhombus | ½ × d₁ × d₂ | 4a |
| Ellipse | π a b | Ramanujan approximation |
Worked example
A circle of radius 5 m: area = π × 25 ≈ 78.54 m², circumference ≈ 31.42 m.
Frequently asked questions
Irregular plot of land?
Split it into rectangles and triangles and add their areas.
m² to hectares?
One hectare = 10,000 m². Use the area unit converter.
What value of π is used?
≈ 3.14159; the calculator uses full precision.