Surface Area Calculator
Calculate surface area for cubes, rectangular prisms, cylinders, spheres and cones from their dimensions, with the formula shown for every shape.
Surface Area
150 sq units
SA = 6s²
Last updated: January 2026
How this calculator is verified
Checked by True Calculator automated test suite on
- Formula verified against a published worked example in the automated test suite
- Edge cases (zero, negative, boundary and unit-mismatch inputs) covered by unit tests
The full verification method is on our how we verify page. Found an error? Tell us and we will re-check it.
When to Use This Calculator
A painter in Kanpur must paint the outside of a rectangular box 2 metres long, 3 metres wide and 4 metres high. Entering these dimensions, the calculator sums the six faces: two of 2 by 3, two of 3 by 4 and two of 2 by 4, which is 12 plus 24 plus 16, or 52 square metres in total. A cube of side 4 metres gives a simpler check: six faces of 16 square metres, so 96 square metres. Surface area is always in square units, unlike volume, which is cubic.
How to Use This Calculator
- Step 1: Choose the 3D shape you need the surface area for — cube, cuboid, cylinder, sphere or cone.
- Step 2: Enter the dimensions for that shape, such as length, width and height for a prism.
- Step 3: Pick a unit so the result comes out in square units.
- Step 4: Read the total surface area and, where available, the lateral area and the formula used.
Worked Example
A painter in Kanpur must paint the outside of a rectangular box 2 metres long, 3 metres wide and 4 metres high. Entering these dimensions, the calculator sums the six faces: two of 2 by 3, two of 3 by 4 and two of 2 by 4, which is 12 plus 24 plus 16, or 52 square metres in total. A cube of side 4 metres gives a simpler check: six faces of 16 square metres, so 96 square metres. Surface area is always in square units, unlike volume, which is cubic.
Tips and Common Mistakes
- •Tip 1: Surface area is measured in square units, so do not compare it with volume, which uses cubic units.
- •Tip 2: For cylinders, the total area is the curved side plus both circular ends, so say whether the tank is open or closed.
- •Tip 3: When ordering paint, add a little extra for overlaps, touch-ups and wastage at corners.
- ✗Mistake 1: Counting only three faces of a rectangular prism; every prism has six faces, two of each size.
- ✗Mistake 2: Omitting the two circular ends of a cylinder; only the curved part is the lateral area.
Frequently Asked Questions
What is the difference between surface area and volume?
Surface area is the total area of all the faces of a 3D shape, measured in square units, while volume is the space inside it, measured in cubic units. A box 2 m × 3 m × 4 m has 52 m² of surface area but 24 m³ of volume.
How do I calculate the surface area of a cylinder?
Total surface area is 2πr(r + h) — the curved side plus both circular ends. A cylinder with radius 0.7 m and height 1.5 m has about 9.68 m² in total, of which the curved part is about 6.6 m². Choose open or closed to include or exclude the ends.
How much paint do I need for a room?
Find the total wall area, subtract doors and windows, then divide by the coverage of the paint. One litre of interior emulsion covers roughly 9–10 m² (about 100 sq ft) per coat, so a 40 m² wall area needs about 4 litres per coat.
Why do paint and tile shops quote in square feet?
Construction materials in India are usually priced per square foot. The calculator returns square metres, so multiply by 10.764 to convert — 52 m² is about 560 sq ft.
Which shapes does the calculator support?
Cube, cuboid (rectangular prism), cylinder, sphere and cone, with the formula shown for each shape. It returns the total surface area and, where available, the lateral area as well.
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