Find how much liquid fills a length of pipe or hose — useful for flushing and disinfecting water lines, filling heating systems, and sizing antifreeze or chemical doses.
Use the inside diameter. Nominal pipe sizes (such as “2-inch pipe”) can differ from the true bore depending on the material and schedule.
Formula
Volume = π × (Inside diameter ÷ 2)² × Length
With dimensions in inches, divide cubic inches by 231 to get US gallons.
Worked example
100 ft of pipe with a 2-inch bore holds π × 1² × 1,200 = 3,770 in³, or about 16.3 gallons (61.8 L).
Frequently asked questions
How many gallons per foot are in a 1-inch pipe?
About 0.041 gallons per foot (0.51 L/m) for a true 1-inch inside diameter.
Does pipe material matter?
Only through the inside diameter. Thick-walled pipe of the same nominal size has a smaller bore and holds less.
Last updated · Calculations checked by automated tests· Editorial policy