Pipe Volume Calculator
Find how much water a pipe holds. Enter the inner diameter in inches and the run length in feet to get the volume in cubic inches, US gallons and liters.
How to calculate pipe volume
- Measure the inner (bore) diameter of the pipe in inches, not the outside diameter.
- Measure the total length of the pipe run in feet.
- Enter both values to read the volume in cubic inches, gallons and liters.
Examples
100 ft of half-inch pipe
0.5 in inner diameter, 100 ft long
About 235.6 cubic inches, 1.02 gallons (3.86 liters)
Frequently asked questions
How do I find the volume of water in a pipe?
Treat the pipe as a cylinder. Multiply pi by the inner radius squared by the length, all in inches, to get cubic inches, then divide by 231 to get US gallons.
Should I use the inner or outer diameter?
Use the inner (bore) diameter, since only the inside holds water. The outer diameter includes the pipe wall and would overstate the volume.
Why does pipe volume matter?
It tells you how much water sits in a line, which you need for flushing, purging air, dosing antifreeze, and estimating how long it takes to drain or heat the water.
How many gallons are in a 100 foot garden hose?
A common 0.625 inch inner diameter hose at 100 feet holds about 1.6 gallons. Enter your hose diameter and length to get an exact figure.
Does length convert from feet correctly?
Yes. The length in feet is multiplied by 12 to work in inches, so the radius and length share the same unit before the volume is computed.
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