Gas cylinder

Gas Cylinder Volume

Find the physical internal volume of a gas cylinder shell in litres. (Stored gas at pressure is a separate calculation.)

A gas cylinder has two different 'volumes': the physical space inside the steel shell, and the much larger amount of gas it holds once compressed. This gas cylinder volume works out the first — the internal shell volume in litres — from the outside dimensions.

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.

How the calculation works

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.

How the volume is worked out

The volume of a cylinder is:

V = π r² h

A worked example

Worked example. Take a cylinder with a diameter of 20 cm (so a radius of 10 cm) and a height of 40 cm. The base area is π × 10² = 314.16 cm², and multiplying by the height gives a volume of about 12.57 litres (12,566 cm³ · 3.32 US gallons).

This is the physical internal volume of the cylinder body. The amount of gas stored inside depends on pressure and is a separate, much larger figure.

Conversions use standard factors: 1 US gallon = 231 in³, 1 Imperial gallon = 4.54609 L, 1 litre = 1000 cm³.

Follow-on questions, answered

Most jobs need one or two more things once the volume lands. The common follow-ups, with the numbers you need, are below:

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.

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.

Where people use this

People reach for this in a range of situations:

Checking a geometry homework answer
Sizing a barrel, drum or planter
Estimating pipe or duct volume
Planning a DIY water feature

Where people go wrong

Two things trip people up: squaring the wrong number, and forgetting that the answer is cubic. If a result looks four times too big or too small, you have probably swapped radius and diameter somewhere, so it is always worth re-reading the measurement you are least sure of. It also helps to glance at the equivalent units; if the litre and gallon figures are both off by the same factor, the input is the culprit, not the maths.

One result, every unit

Because volume units are where most errors creep in, the tool does the converting for you. Enter your measurements once and every common unit appears together, from millilitres up to cubic metres and across to US and Imperial gallons. Pick whichever the task calls for and lift the rest from the list; nothing needs a second calculation. The result also updates live as you change a measurement, so you can compare two sizes quickly without starting over.

Keep going

Once you have your answer you may also want to work in tank capacity litres & liters cylinder volume. These related calculators pick up where this one leaves off:

In short: measure the width and the height, keep them in the same unit, and the tool turns them into a volume you can read in litres, gallons, cubic feet or anything else, with the working shown so you can trust it. If a result ever looks off, re-enter the measurement you are least sure of, or switch to the diameter input and let the tool halve it for you, which catches the most common error before it matters.

Good to know

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.

Does this work for a tank or a pipe?

Yes. A solid tank uses the standard mode; for a pipe or tube use the hollow mode, which subtracts the bore. For a tank on its side, use the horizontal mode.

What volume does a gas cylinder have?

There are two figures: the physical internal volume of the steel shell (what this tool finds, in litres) and the volume of gas it holds at pressure, which is far larger and depends on the fill pressure.

Can this tell me how much gas is inside?

Not directly — stored gas depends on pressure and temperature. This calculator gives the water-capacity-style internal volume of the cylinder body.

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.