Hollow tube & pipe
Formula for Volume of a Hollow Cylinder
Outer wall minus the bore: get the material volume of a pipe or the liquid it can hold, from outer and inner diameters.
A pipe or tube is a cylinder with a hole down the middle, so its volume is the outer cylinder minus the inner one. This formula for volume of a hollow cylinder asks for the outer and inner diameters and returns the wall (material) volume, the bore capacity, or both.
A pipe is really two cylinders — the outside and the hole — and almost every practical question is about the difference between them. Whether you are costing the metal, sizing the flow, or estimating a coating, you are working with either the wall or the bore, and it pays to be clear which.
Using the calculator
- Measure the outer diameter and the inner (bore) diameter.
- Halve each to get the outer radius R and inner radius r.
- Find the ring area: π (R² − r²).
- Multiply by the length to get the wall (material) volume.
- Read the bore capacity and material volume separately.
Getting an accurate measurement
Confirm the inner diameter is the bore, not the wall thickness. Keep every measurement in the same system, and let the tool convert between units for you.
How the volume is worked out
The volume of a hollow cylinder is:
V = π h (R² − r²)A 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).
Keep the two results apart: the wall (material) volume is the metal or plastic itself, while the bore capacity is what the pipe can carry. They are not interchangeable.
Conversions use standard factors: 1 US gallon = 231 in³, 1 Imperial gallon = 4.54609 L, 1 litre = 1000 cm³.
After you have your answer
To save you a second search, here are the related answers people most often want straight after this calculation:
What if it is a very thin tube?
The same formula applies however thin the wall — the material volume simply becomes small next to the bore, which the breakdown makes clear at a glance.
How much can the pipe carry?
The bore capacity — the space inside — is listed separately from the wall material in the result, so you can read both from a single calculation.
How do I get the weight of the pipe?
Use the wall (material) volume, not the bore, and multiply by the material density. Tick estimate weight and the tool does it once you enter a density.
What is the wall thickness from the diameters?
Wall thickness is the outer diameter minus the inner diameter, divided by two. Enter both diameters and the tool uses them to separate metal from bore automatically.
Where people use this
People reach for this in a range of situations:
- Estimating the steel in a run of pipe
- Working out how much a tube can carry
- Costing anti-corrosion coating from surface and volume
- Comparing wall thickness options
Common mistakes to avoid
The classic error is mixing up the inner diameter with the wall thickness — they are not the same, and swapping them changes the answer completely. It also matters which figure you carry forward: use the wall volume for weight and material, and the bore volume for flow or capacity. The tool keeps them separate so you can pick correctly.
Getting the number in the unit you need
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 solid rod & bar. 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
Must the inner diameter be smaller than the outer?
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.