Free Online Volume and Surface Area Calculator
Work out the volume and the surface area of ten solids at once, from a cube, box, cylinder and cone to a sphere, pyramid, prism, torus and capsule. Each shape also gives the extras that go with it, such as the slant height of a cone or the curved surface of a cylinder on its own, with every formula shown.
The sum runs in your browser. Nothing you type is sent anywhere.
🧊 The measurements
Only the boxes this solid needs are shown. Every length must be in the same unit; the volume then comes out in that unit cubed and the surface area in it squared.
The formulas for this solid, with your own numbers in them.
| What | Formula | With your numbers |
|---|
| When | Calculation | Actions |
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Number formatting
Rounding only changes what you see. The sum itself always runs at full precision, so a rounded number never feeds into the next step.
Display
Full screen hides the page around the tool. Press Escape, or the button in the bar, to come back.
History
Your data
Settings, history and saved setups live in this browser and nowhere else. There is no account and no server, which also means clearing them here is final.
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How to Find Volume and Surface Area
Three steps, and the third is the one worth reading.
What to Know About Solids
Why the two go together, and where the formulas trip people up.
Key Features & Capabilities
What it does, and what it deliberately does not.
About Volume and Surface Area
Volume is how much a solid holds and surface area is how much skin it has. Both are determined by the same handful of measurements, which is why this page gives them together: asking for the radius and height of a cylinder on one page for its volume and again on another for its surface is wasted effort and an extra chance to mistype.
The relationship between the two is more interesting than either on its own. Surface area grows with the square of a length while volume grows with the cube, so a shape scaled up by a factor of two has four times the surface and eight times the volume. Everything that happens through a surface, heating, cooling, evaporating, dissolving, coating, therefore gets relatively slower as a shape gets larger. That is why a small animal eats constantly and a large one does not, and why ice cubes melt faster than an iceberg. The surface to volume ratio shown on the page is that comparison in one number.
The formulas themselves hold two traps. The first is the cone, which has two different heights: the perpendicular height from apex to base centre, used for the volume, and the slant height down the sloping side, used for the curved surface. They are different numbers and swapping them is the standard mistake, so the slant height is computed from the perpendicular one and displayed rather than being requested.
The second is partial surfaces. Real questions rarely ask for the total. A label for a tin needs the curved part of the cylinder without the ends. An open tank needs the sides and the base without the lid. A cone’s net needs the curved part separately from the circular base. Those pieces are given as extras here, because working them out from a total is exactly the step people come to a calculator to avoid.
One practical note. Every length entered has to be in the same unit. The volume then comes out in that unit cubed and the surface area in it squared. Mixing centimetres and metres in the same shape is the most common source of an answer that is wrong by a factor of a thousand, and no calculator can detect it, because the numbers themselves look perfectly reasonable.
Frequently Asked Questions
Shapes, units, slant heights and curved surfaces.
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