Pipe Volume Calculator

A pipe is a cylinder, so its internal volume is pi times the inside radius squared times the length. The radius is half of the inside diameter, not the outside diameter, because the pipe wall does not hold water. To get US gallons, divide the volume in cubic inches by 231, since one US gallon is exactly 231 cubic inches.

Nominal pipe size is a label, not the true bore. A 1 inch Schedule 40 steel or PVC pipe actually has about a 1.049 inch inside diameter, while 1 inch copper Type L is closer to 1.025 inches. The calculator stores published inside diameters for each material and schedule, so picking a nominal size loads the correct bore for you. In custom mode you can type a measured inside diameter directly.

Volume per foot is the amount of fluid one linear foot of pipe holds, in gallons or liters. It is the standard figure for purging lines, dosing chemicals, sizing water changes, and adding antifreeze, because you usually know the run length in feet. For example, 1 inch Schedule 40 pipe holds about 0.0449 gallons per foot, so a 50 foot run holds roughly 2.24 gallons.

Yes. In nominal mode you choose between steel or PVC at Schedule 40 and copper Type L, and the calculator applies the matching inside diameter. For any other material, schedule, or tubing, switch to custom mode and enter the actual inside diameter you measure or look up. The volume math is identical once the bore is known.

The calculator multiplies the volume in gallons by about 8.34 pounds per gallon, the weight of fresh water near 60 degrees F. So a 100 foot run of 2 inch Schedule 40 pipe holding about 17.4 gallons weighs roughly 145 pounds when full. Warmer water is slightly lighter and chemical solutions can differ, so treat the weight as a close estimate.