Solve a dimension
Height of Cylinder Calculator
Work backwards: enter the volume you need plus one dimension, and solve for the missing height, radius or diameter.
This height of cylinder calculator runs the calculation in reverse. Tell it the volume you are aiming for and one dimension you already have, and it returns the missing measurement.
Working backwards is surprisingly common: you know the capacity you need and one dimension you are stuck with, and you have to find the rest. Rearranging the volume formula does the job, and it is far quicker than guessing dimensions and re-checking the volume each time.
The maths in one line
The volume of a cylinder is:
h = V / (π r²) · r = √(V / π h)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).
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.
Using the calculator
- Choose which dimension you need — height, radius or diameter.
- Enter the target volume you want the cylinder to hold.
- Enter the one dimension you already know.
- 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.
Once the result is in
To save you a second search, here are the related answers people most often want straight after this calculation:
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.
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.
Where people go wrong
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
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 volume formula tank capacity cylinder volume. These related calculators pick up where this one leaves off:
When this comes in handy
People reach for this in a range of situations:
- Checking a geometry homework answer
- Sizing a barrel, drum or planter
- Estimating pipe or duct volume
- Planning a DIY water feature
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.
Good to know
What units can I use?
Is the volume of a cylinder squared or cubed?
Does this work for a tank or a pipe?
How do I find the height of a cylinder from its volume?
h = V ÷ (π r²). Enter the target volume and the radius above, and the height is solved for you.How do I find the radius from volume and height?
r = √(V ÷ (π h)). The tool can also return the diameter, which is simply twice the radius.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.