About the Cylinder Calculator
A cylinder is a solid with two equal circular ends joined by a curved side, like a tin can, a pipe, a drum or a water tank. This calculator takes its radius or diameter and its height, and gives the volume, the area of one end, the curved side area and the total surface area. It also converts the volume to litres and US gallons, which makes it useful for estimating how much a barrel, rain butt or round tank can hold. Choose millimetres, centimetres, metres, inches or feet, and the units are converted for you.
Updated October 2026
How to use the Cylinder Calculator
- 1Select the unit you measured in.
- 2Say whether you know the radius or the diameter, and type it in.
- 3Type the height of the cylinder, in the same unit.
- 4Read the volume, with its size in litres and US gallons below it.
- 5Check the surface area lines if you need to paint or wrap the outside.
A worked example for a rain barrel
A barrel is 60 cm across and 90 cm tall. The radius is 30 cm, so the volume is π × 900 × 90, about 254,470 cubic centimetres. That is 254 litres, or 67 US gallons. Allow some room at the top for overflow, so the usable capacity is a little less.
Accuracy depends on how carefully you measure. A tank with a 1 cm error in radius changes its volume by roughly 4 percent if the radius is 50 cm, so measure across the widest point twice and average the readings. If the sides taper slightly, take the radius at the middle height, which gives a good approximation of the true capacity. For liquids, remember that the usable volume is the part below the overflow or outlet, not the full geometric volume.
Where cylinder sums are useful
- Water tanks, drums, cans and pipes.
- Concrete poured into round footings and columns.
- Packaging: the label area of a tin is the side area.
- Cooking: the volume of a round cake tin or pot.
Measuring tips
Measure inside dimensions for capacity and outside dimensions for surface area. Wrap a tape around the cylinder and divide by pi to get the diameter if you can't reach across.
Compare with the Volume Calculator, the Cone Calculator and the Sphere Calculator, or use the Concrete Calculator to turn a footing volume into bags.
Features
- Volume, base area, side area and total surface area
- Radius or diameter input
- Litres and US gallons
- Millimetres, centimetres, metres, inches and feet
- Rejects zero and negative sizes
- Quick copy of the result line
Frequently asked questions
What is the formula for the volume of a cylinder?
Volume equals pi times the radius squared times the height. A cylinder with a 5 cm radius and a 12 cm height holds π × 25 × 12, about 942.5 cubic centimetres, which is 0.94 litres.
How do I find the surface area of a cylinder?
Add the curved side, 2 × π × radius × height, to the two circular ends, each π × radius squared. Together they give the total surface area, which is the amount of material needed to cover the whole outside.
How do I get litres from a cylinder volume?
Convert the volume to cubic centimetres and divide by 1,000, because a litre is 1,000 cubic centimetres. The calculator does this automatically for any unit you choose.
Do I use the radius or the diameter?
Either. The radius is half the diameter. If you measured across the circle at its widest point, select diameter and the calculator halves it for you. Mixing the two is the most common mistake in cylinder sums.
Can I use it for a horizontal tank?
It gives the volume of the full cylinder whichever way it lies. A part-filled horizontal tank needs a segment formula, but a full or exactly half-full tank can be worked out by halving this result.
What about hollow pipes?
Calculate the outer cylinder and the inner cylinder separately and subtract. The difference is the volume of the pipe wall material, and the inner cylinder alone is the capacity for fluid inside.