Pipe Volume Calculator
Find how much water or other liquid a pipe holds from its diameter and length, in gallons, liters and cubic feet, plus the volume per foot.
A pipe holds pi times the inside radius squared times its length. A 4 in inside diameter pipe 100 ft long holds 65.28 US gallons, or 247.11 liters, which is 0.6528 gallons per foot. Use the inside diameter: the wall takes up space that holds no liquid.
Results are the geometric volume of a straight, perfectly round bore, rounded for display. They leave out fittings, bends, valves, tanks and any lining or buildup inside the pipe, and the size printed on a pipe may be a nominal size rather than the actual inside diameter, so measure or look up the true bore for your pipe.
Liquid the pipe holds
65.28 US gallons
- In liters
- 247.11 L
- In cubic feet
- 8.73 cu ft
- Per foot of pipe
- 0.6528 gal
- Per meter of pipe
- 8.11 L
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About the Pipe Volume Calculator
The inside of a pipe is a long, thin cylinder, so its capacity is the circle of the bore times the length. Units are the usual stumbling block. Pipe diameters are usually in inches or millimeters and runs in feet or meters, so the calculator takes each in its own unit and converts exactly: a 4 in bore over 100 ft is 8.73 cubic feet, or 65.28 US gallons, using 231 cubic inches to the gallon. The second is which diameter to use. Only the inside diameter counts toward what the pipe holds, and the size printed on a pipe is often a nominal or outside size rather than the bore. If you know the outside diameter and the wall thickness, switch modes and the calculator subtracts two walls: a 4.5 in outside diameter with a 0.237 in wall leaves a 4.026 in bore, which holds 66.13 gallons over 100 ft. Because volume grows with the square of the diameter, halving the bore cuts the capacity to a quarter: a 2 in bore 50 ft long holds 8.16 gallons, and a 3/4 in bore 20 ft long holds only 0.46. In metric, a 110 mm bore 30 m long holds 285.1 liters.
Frequently asked questions
How many gallons are in a foot of pipe?+
It depends on the inside diameter: pi x (diameter / 2) squared x 12 in, divided by 231 cubic inches per gallon. A 4 in bore holds 0.6528 gallons per foot, and a 2 in bore 0.1632, a quarter as much.
Should I use the inside or outside diameter?+
The inside diameter, because only the bore holds liquid. If you only know the outside diameter, enter it with the wall thickness and the calculator works out the bore: 4.5 in outside with a 0.237 in wall is a 4.026 in bore.
How do I calculate pipe volume in liters?+
Work in centimeters: pi x (inside diameter / 2) squared x length gives cubic centimeters, and 1,000 of them make a liter. A 110 mm bore 30 m long holds 285.1 liters, about 9.5 liters per meter.
Why does a slightly bigger pipe hold so much more?+
Capacity grows with the square of the diameter. Doubling the bore from 2 in to 4 in multiplies the volume by four, which is why a 4 in bore holds 65.28 gallons per 100 ft while a 2 in bore holds about 16.32.
Cylinder volume: Weisstein EW, "Cylinder," MathWorld. Units: NIST Handbook 44, Appendix C (1 in = 2.54 cm, 1 US gallon = 231 cubic inches).
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