Hollow tube & pipe

How to Calculate Volume of a Tube

Outer wall minus the bore: get the material volume of a pipe or the liquid it can hold, from outer and inner diameters.

This how to calculate volume of a tube keeps two very different numbers apart: the solid material in a pipe wall, and the space inside the bore. Enter outer and inner diameters plus length, and you get each one clearly labelled.

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.

The formula behind it

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.

How to work it out

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.

Once the result is in

The figure above is usually the start, not the finish. These are the questions that tend to come next, answered here so you do not have to run another search:

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.

What to watch out for

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.

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.

What to work out next

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:

Volume Tube Calculator Cylindrical Pipe Volume Formula Hollow Cylinder Volume Volume of Hollow Cylinder Calculator Calculate Volume of a Hollow Cylinder Volume of a Tube Calculator

Common uses

It comes in handy across quite different tasks:

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

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 difference between material volume and capacity?

Material volume is the solid in the wall; capacity is the empty space in the bore. A pipe's coating budget uses material volume; what it carries uses the bore capacity.

Must the inner diameter be smaller than the outer?

Yes — the bore has to fit inside the wall. The calculator will flag it if the inner value is not smaller.

What is the formula for the volume of a cylinder?

The volume is 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.

Do I use radius or diameter?

Either — just tell the calculator which you are entering. The radius is from the centre to the edge; the diameter is the full width across. The tool converts diameter to radius automatically.

What units can I use?

Any of millimetres, centimetres, metres, inches, feet or yards for the measurements, and you can read the result in litres, gallons, cubic feet, cubic inches and more.

Is the volume of a cylinder squared or cubed?

The result is in cubic units, because volume fills three dimensions. The radius is squared inside the formula only because it forms the flat circular base; multiplying by the height adds the third dimension.