Cubic Inches of a Cylinder

Using the calculator

1. Measure across the circular end — the diameter or radius.
2. If you measured the diameter, halve it to get the radius r.
3. Square the radius and multiply by π to get the base area.
4. Multiply the base area by the height h: V = π r² h.
5. 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.

The formula behind it

The volume of a cylinder is:

A worked example

Worked example. Take a cylinder with a diameter of 3 in (so a radius of 1.5 in) and a height of 8 in. The base area is π × 1.5² = 7.07 in², and multiplying by the height gives a volume of about 0.2 US gallons (57 in³ · 0.9 litres).

Conversions use standard factors: 1 US gallon = 231 in³, 1 Imperial gallon = 4.54609 L, 1 litre = 1000 cm³.

What people work out next

The figure above is usually the start, not the finish. These are the questions that tend to come next, answered here so you do not have to run another search:

Is this the same as engine displacement?

For a single cylinder, yes: the bore radius and the stroke give the swept volume in cubic inches. Multiply by the number of cylinders for total displacement.

What is it in cc (cubic centimetres)?

One cubic inch is about 16.39 cc, so the cm3 figure in the breakdown is the metric version that engine builders usually quote.

How do I turn cubic inches into gallons?

Divide by 231 for US gallons — that is the exact definition of a US gallon — or by about 277.42 for Imperial. Both gallon values are shown with the result.

Where people use this

People reach for this in a range of situations:

• Blueprinting an engine's displacement
• Sizing a small precision reservoir
• Converting a machined bore to gallons

Common mistakes to avoid

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.

Keep going

Once you have your answer you may also want to work in gallons cubic feet volume formula. 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.

Questions people ask