Pro Calculators and Guides
How to Calculate Area, Perimeter, Surface Area and Volume of Common Shapes
Formulas and a calculator for rectangles, circles, triangles, cubes, cylinders, spheres and more, with unit tips.
Saizul Amin15 Oct 2026 · Updated 17 Oct 2026 · 1 min read
Geometry shows up in homework, building work and design. The formulas are short; using the same units is where mistakes happen.
Quick answer
Pick the shape, enter the measurements in one unit, and read the area and perimeter (flat shapes) or the surface area and volume (solids).
Flat shapes
| Shape | Area | Perimeter |
|---|---|---|
| Rectangle | l × w | 2(l + w) |
| Square | s² | 4s |
| Triangle | ½ × b × h | a + b + c |
| Circle | πr² | 2πr |
Solids
| Shape | Surface area | Volume |
|---|---|---|
| Cube | 6s² | s³ |
| Cuboid | 2(lw + lh + wh) | l × w × h |
| Cylinder | 2πr(r + h) | πr²h |
| Sphere | 4πr² | (4/3)πr³ |
| Cone | πr(r + l) | (1/3)πr²h |
Example
A cylinder with radius 5 cm and height 12 cm has a volume of π × 25 × 12 = 942.5 cm³.
Unit tips
- Use the same unit for every measurement.
- Area is in squared units (cm², m²); volume is in cubed units (cm³, m³).
- 1 m³ = 1,000 litres.
Steps
- Choose the shape.
- Enter dimensions.
- Read the results.
Common mistakes
- Using diameter instead of radius for circles.
- Mixing centimetres and metres.
- Forgetting that triangle area uses the perpendicular height.
