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Pipe water capacity Calculator

Calculate the liquid held inside a circular pipe.

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How to use this calculator

Your measurements

Choose the unit beside each measurement. Changing a unit converts your value.

Item name (optional)

View your estimate

Use internal diameter, not nominal pipe size or outside diameter. Assumes the pipe is completely full.

YOUR ESTIMATE

Internal capacity

9.817L

Internal volume0.01 m³

Same quantity, different units

Internal volume

m³: 0.0098
yd³: 0.0128
ft³: 0.3467

Calculated from your measurements.

PLAN YOUR PROJECT COST

Pricing calculator

Use your supplier’s rate or enter a quoted total. Save each estimate to your project and print everything together.

What are you pricing?

Price is per

Price (optional)

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Your selected quantity already includes any allowance shown in that result. Check whether you are pricing individual items or whole packs. Delivery, tax and labour are not added automatically. A quoted total applies only to this saved calculation.

Pipe water capacity Calculator: measuring notes and method

Sum different pipe sections

Calculate each diameter and length separately before adding capacity. Fittings, appliances and tanks need their own volumes.

CHECK A PRACTICAL EXAMPLE

Internal diameter changes stored water

Both fully filled straight pipe sections are 20 m long. Compare actual internal diameters.

20 mm internal diameter

Internal capacity: 6.283 L
Internal volume: 0.006 m³

Try these inputs

25 mm internal diameter

Internal capacity: 9.817 L
Internal volume: 0.01 m³

Try these inputs

Capacity follows diameter squared. Nominal pipe size may differ from the bore; fittings and connected equipment need separate capacities.

Fixed comparison in metric units. Values are illustrative unless linked to a recorded project; changing the calculator above does not change this example.

Formula

Capacity = π × (internal diameter ÷ 2)² × pipe length. Convert cubic volume to litres or US gallons.

Worked examples in metric and imperial units

Illustrative values match Reset example and stay fixed when you edit the calculator. Both columns describe the same calculation; converted inputs are rounded.

Metric worked example

Internal pipe diameter: 25 mm
Pipe length: 20 m

Internal capacity: 9.8175 L

Imperial worked example

Internal pipe diameter: 0.9843 in
Pipe length: 65.6168 ft

Internal capacity: 2.5935 US gal

Follow the calculation

Lengths in this working are in metres.

Internal volume = π × (0.025 ÷ 2)² × 20 = 0.009817 m³.
Multiply cubic metres by 1,000 to obtain litres.

Reviewed 19 October 2026. How calculations are checked · Report a correction

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Pipe flow from velocity CalculatorConvert pipe diameter and average velocity into flow.Tank fill time CalculatorEstimate the time to fill a tank at a known flow rate.Drain fall & gradient CalculatorCalculate the gradient of a measured drain run.

PRACTICAL READING

Understand the inputs. Check the order.

Measurement methods and worked examples to use alongside this calculator.

Separate pipe capacity, flow rate and tank filling timeVolume stored in a pipe is different from water moving through it.
Schedule pipe falls and stock cuts independentlyLevel difference checks do not determine the lengths and fittings to purchase.
Check units before multiplying measurementsAvoid the square and cubic conversion mistakes that can make a plausible-looking estimate wrong.
Build a measurement register you can check laterRecord where each number came from before it becomes part of a material order.

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