How to use the cylinder volume calculator
- 1 Choose whether you know the radius or diameter.
- 2 Enter the radius or diameter and the height.
- 3 Choose the unit.
- 4 Read the volume in cubic units, gallons and liters, and the surface area.
Worked example
A round tank 2 feet across (radius 1 foot) and 4 feet tall. The volume is V = πr²h = π × 1² × 4 = 12.5664 cubic feet, which is 355.84 liters or 94.0 US gallons. The base area is 3.1416 square feet and the total surface area is 31.4159 square feet.
Getting tank volumes right
- Use inside measurements for capacity.
- Halve the diameter if you measured across.
- Check the unit: inches and feet give very different numbers.
- Leave headroom: tanks are rarely filled to the brim.
Find the radius with the Circumference Calculator, convert capacity with the Volume Converter and Gallons to Liters, and order concrete for a column with the Concrete Calculator.
Features
Gallons and liters
Tank capacity in US gallons and liters, not just cubic units.
Radius or diameter
Use whichever you measured.
Surface area too
Lateral and total surface area for painting or wrapping.
When to use it
Water tanks and barrels
Find how many gallons a round tank holds. Convert units with the Volume Converter.
Concrete columns
Order concrete for a round post or pier with the Concrete Calculator.
Homework
Check cylinder problems step by step. Find the circle first with the Circumference Calculator.
Pipes
Work out how much water a length of pipe holds.
Related Math tasks
Frequently asked questions
What is the formula for the volume of a cylinder?
V = πr²h, where r is the radius of the base and h is the height. It is the area of the circular base times the height.
How do I find the volume from the diameter?
Halve the diameter to get the radius, then use V = πr²h. A cylinder 2 feet across and 4 feet tall holds π × 1² × 4 = 12.57 cubic feet.
How many gallons are in a cylinder?
One cubic foot is about 7.48 US gallons, so multiply cubic feet by 7.48. The calculator converts automatically: 12.57 cubic feet is about 94 gallons.
How many liters are in a cubic foot?
28.317 liters. One cubic meter is 1,000 liters and one cubic inch is 0.016387 liters.
How do I find the volume of a horizontal tank?
A full horizontal tank has the same volume, using its length as the height. A partly filled horizontal tank needs a different formula for the liquid depth.
What is the surface area of a cylinder?
Lateral area is 2πrh (the curved side) and total area adds the two circular ends: 2πr² + 2πrh.
How do I measure the radius of a round tank?
Measure the distance around it (circumference) and divide by 2π, or measure straight across the top and halve it.
Does wall thickness matter?
For capacity, use the inside measurements. Outside measurements include the wall and overstate the volume.
What is the volume of a cone compared with a cylinder?
A cone with the same base and height holds one third of the cylinder: V = ⅓πr²h.
What is the difference between US and imperial gallons?
A US gallon is 3.785 liters; an imperial (UK) gallon is 4.546 liters. This calculator uses US gallons.
How many gallons does a 55-gallon drum really hold?
A standard drum is about 22.5 inches across and 33.5 inches tall, about 13,300 cubic inches or 57.7 gallons to the brim; it is filled to about 55.
How do I find the height needed for a certain volume?
Divide the volume by the base area: h = V ÷ (πr²).
Can I use this for a round swimming pool?
Yes. Use the pool's radius and the average water depth as the height to get its volume in gallons.
Built and reviewed by Hamza Farooq, founder and lead developer
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