Volume Calculator

A cubic metre is 1,000 litres, and a litre is 1,000 cubic centimetres — so a cubic centimetre and a millilitre are the same volume, which is why syringes are marked cc in some countries and ml in others. A cubic metre is therefore a million cubic centimetres. The mistake that catches people is converting the length factor without cubing it: a foot is 0.3048 metres, but a cubic foot is that figure cubed, about 0.0283 cubic metres, or 28.3 litres. Miss the cube and you are wrong by more than thirty times over. An inch is 2.54 centimetres along an edge but roughly 16.4 cubic centimetres of space.

Measure the inside, and stop at the water line rather than the rim. Ten-millimetre glass takes twenty millimetres off both the length and the width, and a tank is normally filled a couple of centimetres down so nothing slops over, so the capacity printed on the box and the water actually in the tank are rarely the same number. Then subtract what is already in there — substrate, rocks and large ornaments displace their own volume, and a deep sand bed eats a real share of a small tank. If you dose anything by volume, that reduced figure is the one to work from.

No, and the difference is large enough to ruin a calculation. A US liquid gallon is 3.785 litres; an imperial gallon, still in use in the UK, is 4.546 litres — around a fifth larger. The pints differ too: 16 US fluid ounces against 20 imperial ones, with the ounces themselves not quite equal. The gallons figure shown here is the US one. So when you are reading a British spec sheet, an old recipe or a fishkeeping thread, work out which gallon is meant before trusting the number, because tank capacities in particular get quoted in both without ever being labelled.

Split it. Most awkward objects are two or three simple solids added together or subtracted — a silo is a cylinder with a cone on top, an L-shaped room is two boxes, a hollow pipe is the outer cylinder minus the inner one. Anything with a constant cross-section, like a triangular prism or a length of guttering, is that cross-sectional area multiplied by the length, which is the same rule that gives a cylinder pi times radius squared times height. A pond with sloping sides is a frustum rather than a box. For a genuinely irregular object, water displacement beats arithmetic.

A capsule is a cylinder with a hemisphere closing each end — a propane tank, a horizontal air receiver, a pill. Its volume is the cylinder plus one whole sphere, because two hemispheres of the same radius make one. The height is exactly what people get wrong: the formula wants the straight middle section only, not the overall length of the object, which is why the field asks for the height of the straight section rather than the height. If your tape reads end to end, subtract the radius twice — once per dome — before entering it, or the answer is too large by a full sphere.

Work it out in cubic metres, then convert to litres, because bagged compost is sold by the litre nearly everywhere. A bed two metres by one, filled to a depth of thirty centimetres, is 0.6 cubic metres — 600 litres, or a dozen fifty-litre bags, which is more than most people expect. Loose soil delivered in bulk is priced by the cubic metre or by the tonne, and the tonne figure shifts with how wet the load is on the day. Order slightly over, since soil settles, and deduct any logs, rubble or old turf going into the base.

A box of pillows fills a van like a box of books, so carriers bill on whichever is greater: the actual weight or a volumetric one worked out from the size. The method is the same everywhere — multiply length by width by height in centimetres, then divide by a divisor the carrier publishes. Five thousand is the commonest, but the number differs between companies and between services and does get revised, so take it from your own account rather than from a forum post. Measure the packed box on the outside, bulges included, and round up, because they do.

No. Nothing leaves the page — the calculation runs entirely in your browser, with no request to a server anywhere in it, so the dimensions of your tank, your parcel or your building are not transmitted, stored or logged, and there is no account to make and nothing to delete afterwards. The one thing worth knowing is the address bar. The shape, the unit and every dimension are written into the URL as you type, which is what makes a calculation shareable as a link — but it also means those numbers travel with the link. If the measurements are sensitive, copy the result rather than pasting the URL into a chat.