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Volume Calculator
Pick a shape, enter its dimensions, and get its volume instantly — in your units plus cubic feet, cubic metres, litres and US gallons, so the same answer works for a moving box, a water tank, or a bag of soil.
For the pyramid, height is the vertical height from the base to the apex — not the slanted edge. For the sphere, enter either the radius or the diameter; if both are given, the radius wins. Conversions: 1 cubic foot = 7.48052 US gallons = 28.3168 litres; 1 cubic metre = 1,000 litres = 264.172 US gallons.
How it works
Box: length × width × height. Cube: side³. Cylinder: πr²h — the area of the circular base times the height. Sphere: (4 ÷ 3)πr³. Cone: (1 ÷ 3)πr²h — exactly one third of the cylinder with the same base and height. Pyramid: (base length × base width × height) ÷ 3 — one third of the box with the same base and height. Conversions use 1 ft = 0.3048 m exactly, so 1 cu ft = 0.0283168 cu m, 1 cu m = 1,000 litres, and 1 US gallon = 3.78541 litres. Worked example: a cylinder of radius 2 ft and height 5 ft has volume π × 2² × 5 = 62.83 cu ft, which is 62.83 × 7.48052 = 470.0 US gallons — about the size of a large home water tank.
Frequently asked questions
How many gallons is a cubic foot of water?
One cubic foot holds 7.48052 US gallons, and a US gallon of water weighs about 8.34 lb — so a cubic foot of water weighs about 62.4 lb. That weight is why full water tanks need a solid, level base.
Why is a cone one third of a cylinder?
For the same circular base and height, the cone tapers to a point, and the volume works out to exactly one third — the same reason a pyramid is one third of its box. It holds for any base shape: volume = (base area × height) ÷ 3.
What is the difference between US and imperial gallons?
A US gallon is 3.78541 litres; an imperial gallon (UK) is 4.54609 litres, about 20% larger. This calculator uses US gallons throughout, as labelled.
How do I find the volume of an irregular container?
Fill it with a known volume of water (a measuring jug, or a 5-gallon bucket counted as you pour) — that is the most accurate method. For an irregular solid, submerge it in a full container and measure the water that overflows.
Should I use radius or diameter for a cylinder?
Either works as long as you are consistent: radius is half the diameter. Measure across the widest point of a round tank to get the diameter, then halve it for the radius this calculator expects.