Cylinder volume
Volume Calc Cylinder
Enter a radius or diameter and a height to get an instant, accurate cylinder volume in any unit — with the formula and every step shown.
Whether you are checking a homework answer, sizing a water butt or working out how much a length of pipe holds, the volume calc cylinder above gives you a reliable number in seconds. Nothing to install, no sign-up, and the formula is shown so you can see exactly how the result is reached.
The reason this shape earns a dedicated tool is that its two measurements are easy to get wrong. Confusing radius with diameter doubles your answer; mixing inches with centimetres throws it out completely. Keeping each measurement labelled, and letting the tool convert, removes both traps before they cost you.
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.
The formula behind it
The volume of a cylinder is:
V = π r² hA worked example
Worked example. Take a cylinder with a diameter of 20 cm (so a radius of 10 cm) and a height of 40 cm. The base area is π × 10² = 314.16 cm², and multiplying by the height gives a volume of about 12.57 litres (12,566 cm³ · 3.32 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.
Once the result is in
To save you a second search, here are the related answers people most often want straight after this calculation:
How do I find a missing dimension?
If you know the volume you need and one measurement, the reverse-solver returns the height, radius or diameter that matches it.
Can I get the weight too?
Tick estimate weight, pick a material, and the calculator multiplies volume by density to show the mass in kilograms and pounds.
What will the volume be in gallons or litres?
You do not have to choose up front. The result lists litres, US gallons, Imperial gallons, cubic feet and more together, so you can switch the main unit whenever you like.
What if I have the diameter, not the radius?
Toggle the base input to diameter and the tool halves it for you. There is also a circumference option for when that is all you were able to measure.
When this comes in handy
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
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
Showing every unit at once is about speed and safety: you see the answer in litres, gallons and cubic feet side by side, so there is no chance of applying the wrong conversion factor. Change the output unit at the top to make any of them the headline figure, switch the precision to exact if you want the value in terms of pi, and use copy-result to paste a tidy summary wherever you need it.
What to work out next
Once you have your answer you may also want to work in gallons litres & liters volume formula. These related calculators pick up where this one leaves off:
The bottom line: with the radius or diameter and the height, the volume follows immediately, and the breakdown lets you hand the same number to anyone in the unit they prefer. Measure inside dimensions for anything that holds liquid, leave a little headspace at the top of a real container, and treat the geometric figure as a clean maximum rather than the final word on usable capacity.
Frequently asked questions
Is the volume of a cylinder squared or cubed?
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.