Pipe Volume Calculator
How much water a pipe holds from its inside diameter and length, in gallons, litres and ft³, with Schedule 40 sizes, weight and time to fill.
A pipe's volume is π × the inside radius squared × its length. 100 ft of 1 in Schedule 40 pipe, which is 1.049 in inside, holds 4.49 US gallons: about 0.045 gallons per foot. In metric, 30 m of pipe 25 mm inside holds 14.7 litres, or 0.49 litres per metre. This calculator works out the volume of one pipe or several, in US gallons, litres and cubic feet, along with the weight of the water. If you enter a flow rate, it shows how long the pipe takes to fill or flush. For US pipe, choose a Schedule 40 size to fill in its standard inside diameter, or type any diameter yourself.
- Volume
- 4.49 US gal
- Per foot
- 0.045 US gal
- Weight of water
- 37.5 lb
- Time to fill or flush
- –
17 L · 0.6 ft³
0.17 L
17 kg
enter a flow rate
How it was worked out
- π × (1.049 in ÷ 2)² × 100 ft = 4.49 US gal
Use the inside diameter: a pipe's nominal size is only a name. The Schedule 40 sizes fill in the standard inside diameters for steel and PVC Schedule 40 pipe; copper, PEX and other pipe have their own, so check the maker's chart.
Common use cases
- Work out how much water to flush through a line before sampling or disinfecting it
- Find the volume of a heating or irrigation loop, to add inhibitor or antifreeze
- Check how much water sits in a long run between the heater and the tap
- Work out the weight of a pipe run full of water
How to use
- Choose feet and inches or metres and millimetres.
- Pick a Schedule 40 size, or enter the pipe's inside diameter.
- Enter the length, and add more pipes if the run has different sizes.
- Enter a flow rate if you want the time to fill or flush.
- Read the volume, the volume per foot or metre, and the weight of the water.
FAQ
How many gallons are in a foot of pipe?
For Schedule 40 pipe: about 0.016 gallons per foot for ½ in, 0.028 for ¾ in, 0.045 for 1 in, 0.174 for 2 in and 0.661 for 4 in. Other kinds of pipe have different inside diameters, so their figures differ.
How many litres are in a metre of pipe?
A pipe 15 mm inside holds 0.18 litres per metre, 25 mm holds 0.49 litres and 100 mm holds 7.85 litres. Multiply by the length for the whole run.
Why does the inside diameter matter so much?
Volume grows with the square of the diameter, so doubling the diameter holds four times as much. A pipe's nominal size is only a name: 1 in Schedule 40 pipe is 1.049 in inside, while 1 in copper or PEX is different again.
How long will it take to flush a pipe?
Divide the pipe's volume by the flow rate. 4.49 gallons at 5 gallons a minute takes about 54 seconds. Enter your flow rate in the calculator to work it out.
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Results are estimates for planning and buying materials, worked out from the figures you enter and typical values (weights, coverage, sizes) that vary by product and supplier. They are not engineering, building or professional advice. Check your local building code, the product maker's instructions and your supplier's figures before you buy or build, and use a qualified professional for structural, electrical and gas work.