Height of a Cylinder Calculator

How to work it out

1. Choose which dimension you need — height, radius or diameter.
2. Enter the target volume you want the cylinder to hold.
3. Enter the one dimension you already know.
4. The tool rearranges V = π r² h and solves for the rest.

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 maths in one line

The volume of a cylinder is:

A worked example

Worked example. Take a cylinder with a diameter of 15 cm (so a radius of 7.5 cm) and a height of 30 cm. The base area is π × 7.5² = 176.71 cm², and multiplying by the height gives a volume of about 5.30 litres (5,301 cm³ · 1.40 US gallons).

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

After you have your answer

To save you a second search, here are the related answers people most often want straight after this calculation:

How tall must a tank be to hold a set amount?

Choose height, enter the volume in gallons or litres and the radius, and the answer is the height needed to reach that capacity.

How wide must it be for a fixed height?

Choose radius or diameter, enter the volume and the height, and the tool returns the width required to hold it.

Does it work in any unit?

Yes. Enter the target volume in gallons, litres or cubic feet and the known dimension in any length unit, and the solved dimension comes back in the length unit you pick.

Which dimension can I solve for?

Height, radius or diameter. Pick one, enter the target volume and the dimension you already know, and the tool rearranges V = pi r squared h for the rest.

Common uses

A few of the jobs it gets used for:

• Checking a geometry homework answer
• Sizing a barrel, drum or planter
• Estimating pipe or duct volume
• Planning a DIY water feature

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.

One result, every unit

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 volume formula tank capacity cylinder volume. These related calculators pick up where this one leaves off:

To sum up, the whole job is two measurements and one formula. Enter them above, pick your unit, and you have an accurate figure plus every equivalent unit beside it. Keep a copy with the copy-result button, save the shareable link if someone else needs the same numbers, and use the history panel to compare a few options without starting from scratch.

Frequently asked questions