Cylinder volume
How Do I Figure Volume of a 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.
A cylinder is one of the friendliest shapes to measure, and the how do i figure volume of a cylinder keeps it that way. Enter what you know — radius or diameter, plus height — and read the volume in litres, gallons, cubic feet or any other unit you need.
Cylinders turn up everywhere once you start noticing them — a tin of beans, a scaffold pole, a rainwater barrel, the barrel of a pump. Because they all share the same simple geometry, one calculation covers the lot, and the only thing that really changes from job to job is the unit you read the answer in.
The maths in one line
The volume of a cylinder is:
V = π r² hA 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).
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
- 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.
After you have your answer
To save you a second search, here are the related answers people most often want straight after this calculation:
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.
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.
Where people go wrong
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.
Reading and converting your result
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 gallons litres & liters volume formula. These related calculators pick up where this one leaves off:
Where people use this
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
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.
Questions people ask
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.