Pipe Volume Calculator
Compute the water volume and weight in a pipe from inner diameter and length, with Schedule 40 presets.
Processed locally in your browser — nothing is uploaded.
Pipe Volume Calculator
Use the actual inner diameter, not the nominal size
Enter the pipe size and length to compute its volume.
About Pipe Volume Calculator
A pipe is a cylinder: π × radius² × length. Enter the inner diameter and run length to get gallons (231 cu in each), liters, and the water's weight at 8.345 lb per gallon. Presets fill in the true inner diameters of common Schedule 40 nominal sizes from 1/2 to 4 inches.
Common uses
- Size an expansion tank or estimate how much water drains from a line
- Figure the weight a filled pipe run adds to its supports
Example
Input
100 ft of 1" Schedule 40 (1.049 in ID)
Output
4.49 gal · 17.0 L · 37.5 lb of water
Limitations
- Nominal pipe sizes differ from actual inner diameters — the presets are Schedule 40; copper and PEX differ
Frequently asked questions
How many gallons of water are in 100 feet of 1 inch pipe?
About 4.49 gallons in Schedule 40, whose true inner diameter is 1.049 in. The same run in 3/4 in pipe holds 2.77 gallons and in 1/2 in pipe just 1.58.
Why isn't a 1 inch pipe actually 1 inch across?
Nominal pipe size is a label, not a measurement. Schedule 40 1 in pipe has an inner diameter of 1.049 in; heavier Schedule 80 keeps the same outside diameter but thickens the wall, shrinking the bore — which is why this calculator asks for the actual inner diameter.
How much does the water inside a pipe weigh?
8.345 lb per gallon of cold water, the figure used here. That's 37.5 lb for 100 ft of 1 in pipe, but about 552 lb for 100 ft of 4 in pipe — enough to matter when you're spacing hangers or loading a ceiling.
Do the Schedule 40 presets work for copper or PEX?
No. Copper and PEX of the same nominal size have smaller bores — 3/4 in Type L copper runs about 0.785 in inside versus 0.824 in for Schedule 40, and PEX is smaller still. Enter the actual inner diameter from the manufacturer's dimension table instead of using a preset.
Is my plumbing data kept private?
Yes. The volume and weight math runs entirely in your browser — pipe sizes, run lengths, and results are never sent to a server or stored.