Cubic feet
Cubic Feet Calculator for Cylinder
Work out the cubic feet inside any cylinder from feet or inches, with the conversion to gallons and litres alongside.
This cubic feet calculator for cylinder answers a practical question: how many cubic feet does this cylinder contain? Enter the diameter and height, and the tool returns ft³, plus the gallon and litre equivalents for good measure.
For bigger cylinders the numbers get unwieldy in small units, which is exactly why cubic feet exists. A round column that would be tens of thousands of cubic inches becomes a handful of cubic feet — easier to picture, and easier to price.
How the calculation works
- Measure across the circular end — the diameter or radius.
- If you measured the diameter, halve it to get the radius r.
- Square the radius and multiply by π to get the base area.
- Multiply the base area by the height h: V = π r² h.
- Convert the result into your preferred unit above.
Getting an accurate measurement
If you can only reach the top, measure the diameter across the opening and halve it. Keep every measurement in the same system, and let the tool convert between units for you.
How the volume is worked out
The volume of a cylinder is:
V = π r² hA worked example
Worked example. Take a cylinder with a diameter of 1.5 ft (so a radius of 0.75 ft) and a height of 5 ft. The base area is π × 0.75² = 1.77 ft², and multiplying by the height gives a volume of about 8.84 cubic feet (66.1 US gallons · 250 litres).
| From | To | Multiply by |
|---|---|---|
| cm³ | litres | 0.001 |
| litres | m³ | 0.001 |
| in³ | US gallons | ÷ 231 |
| ft³ | US gallons | 7.4805 |
| ft³ | litres | 28.3168 |
For anything that holds liquid, measure the inside of the cylinder — the wall takes up space that the contents cannot.
Conversions use standard factors: 1 US gallon = 231 in³, 1 Imperial gallon = 4.54609 L, 1 litre = 1000 cm³.
Follow-on questions, answered
Most jobs need one or two more things once the volume lands. The common follow-ups, with the numbers you need, are below:
What is it in litres or cubic metres?
One cubic foot is about 28.32 litres, or 0.0283 cubic metres, and both appear alongside the cubic-foot result for metric jobs.
Do I measure in feet or inches?
Either. Enter inches on each field if that is how you measured, and the tool converts to feet before giving you the cubic-foot answer.
How many gallons is that?
One cubic foot holds about 7.48 US gallons, and the gallon value is shown in the breakdown, so a cubic-foot figure converts into a fill quantity instantly.
How much concrete should I order?
Suppliers sell by the cubic yard, and 27 cubic feet make one cubic yard. Work in cubic feet here, then divide by 27, or use the cubic-yards mode directly for the order.
Where people use this
It comes in handy across quite different tasks:
- Ordering concrete for a round column or footing
- Sizing a silo or bulk storage cylinder
- Estimating air volume in a round duct
Getting it right
The commonest slip is using the diameter where the formula wants the radius, which on its own quadruples the base area. Close behind is mixing units, such as a radius in centimetres with a height in metres. Keep every length in the same unit, or let the tool convert, and double-check whether you measured to the centre or across the whole width. When a figure looks surprising, that width measurement is almost always where the problem is hiding, so re-read it first.
Getting the number in the unit you need
One number, many units. Whatever you enter, the result lists the same volume as litres, US gallons, Imperial gallons, millilitres, cubic centimetres, cubic inches, cubic feet, cubic yards and cubic metres at the same time. You almost never have to convert by hand: read the figure in the unit your job uses and copy any of the others straight from the breakdown. If you need a shareable version, the copy-link button preserves your exact inputs so a colleague opens the page with the same calculation already filled in.
Related things you might need
Once you have your answer you may also want to work in gallons cubic yards tank capacity. These related calculators pick up where this one leaves off:
In short: measure the width and the height, keep them in the same unit, and the tool turns them into a volume you can read in litres, gallons, cubic feet or anything else, with the working shown so you can trust it. If a result ever looks off, re-enter the measurement you are least sure of, or switch to the diameter input and let the tool halve it for you, which catches the most common error before it matters.
Frequently asked questions
Does this work for a tank or a pipe?
What is the formula for the volume of a cylinder?
V = π r² h — the area of the circular base (π r²) multiplied by the height (h). If you have the diameter instead of the radius, halve it first: r = d ÷ 2.