Calculate Height of a Cylinder

Using the calculator

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 10 cm (so a radius of 5 cm) and a height of 25 cm. The base area is π × 5² = 78.54 cm², and multiplying by the height gives a volume of about 1.96 litres (1,963 cm³ · 0.52 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

Most jobs need one or two more things once the volume lands. The common follow-ups, with the numbers you need, are below:

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.

Where people use this

It comes in handy across quite different tasks:

• 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

Two things trip people up: squaring the wrong number, and forgetting that the answer is cubic. If a result looks four times too big or too small, you have probably swapped radius and diameter somewhere, so it is always worth re-reading the measurement you are least sure of. It also helps to glance at the equivalent units; if the litre and gallon figures are both off by the same factor, the input is the culprit, not the maths.

One result, every unit

Because volume units are where most errors creep in, the tool does the converting for you. Enter your measurements once and every common unit appears together, from millilitres up to cubic metres and across to US and Imperial gallons. Pick whichever the task calls for and lift the rest from the list; nothing needs a second calculation. The result also updates live as you change a measurement, so you can compare two sizes quickly without starting over.

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