Surface Area Calculator
Calculate the surface area of a cube, rectangular box, sphere, cylinder or cone — enter the dimensions and get the area instantly, with the formula shown.
How to calculate surface area
Surface area is the total area of every outer face or curved surface of a 3D shape — think of the amount of paper you would need to wrap it. It is always measured in square units. Each shape has its own formula, so pick the shape above, enter the dimensions, and the calculator applies the right one and shows the formula it used.
Surface area formulas
| Shape | Formula | Inputs |
|---|---|---|
| Cube | 6 × a² | side a |
| Rectangular box | 2(lw + lh + wh) | length, width, height |
| Sphere | 4πr² | radius r |
| Cylinder | 2πr(r + h) | radius, height |
| Cone | πr(r + √(r² + h²)) | radius, height |
For example, a cube with 5-unit sides has a surface area of 6 × 5² = 6 × 25 = 150 square units. A sphere of radius 3 has 4π × 3² ≈ 113.10 square units. Surface area differs from volume, which measures the space inside in cubic units — handy to keep separate when you are painting, wrapping or coating an object versus filling it.
Frequently asked questions
How do you calculate surface area?
Surface area is the total area of all the outer faces or curved surfaces of a 3D shape, measured in square units. Each shape has its own formula — for example a cube is 6 × side², a sphere is 4πr². Pick your shape above, enter the dimensions, and the calculator applies the right formula.
What is the formula for the surface area of a cube?
A cube has 6 equal square faces, so its surface area is 6 × side². For a cube with 5-unit sides that is 6 × 5² = 6 × 25 = 150 square units.
What is the surface area of a sphere?
The surface area of a sphere is 4 × π × radius² (4πr²). For a sphere of radius 3, that is 4 × π × 9 ≈ 113.10 square units. A cylinder is 2πr(r + h) and a cone is πr(r + √(r² + h²)).
What is the difference between surface area and volume?
Surface area measures the outside — the total area you would need to paint or wrap — in square units. Volume measures the space inside, in cubic units. A bigger shape has more of both, but they scale differently: doubling the size multiplies area by 4 and volume by 8.