Pipe Volume Calculator
How much water a pipe holds, in gallons or litres, from its inside diameter and length, with the weight of that water.
Result
Buy 4.08 gal
Uses the inside diameter; fittings and bends add a little more.
- Inside cross-section
- 0.7854 in² (5.0671 cm²)
- Weight of that water
- 34.05 lb (15.44 kg)Estimate
https://calcgallery.com/home-systems/pipe-volume-calculator/
Results are estimates for planning only. Actual needs vary with site conditions, products and workmanship. Always confirm quantities with your supplier and follow local building codes and manufacturer instructions. Read the full disclaimer
How to use the Pipe Volume Calculator
- Enter the pipe's inside diameter, measured or taken from the maker's data sheet.
- Enter the length of the run.
- Read the volume in gallons, cubic feet or litres, and the weight of the water it holds.
The formula
cross-section = π × (inside diameter ÷ 2)²volume = cross-section × lengthA pipe is a long cylinder, so its volume is the area of the bore times the length. Everything is converted to metres before the arithmetic and back to gallons, cubic feet or litres afterwards, so mixing inches and feet is safe.
When it is useful
Knowing what a line holds tells you how long to run a tap to draw fresh water from the main, how much antifreeze a heating loop takes, how much disinfectant a new line needs at a dose your supplier specifies, and how big a bucket catches the water when you drain it. Bends and fittings hold a little more than their straight length, which the page leaves out.
With your numbers
- Volume = π × (inside diameter ÷ 2)² × length
Quick reference
Uses the inside diameter; fittings and bends add a little more.
| Job | Volume in the pipe |
|---|---|
| 1 in inside diameter, 100 ft | 4.08 gal |
| 3/4 in inside diameter, 100 ft | 2.295 gal |
| 1/2 in inside diameter, 50 ft | 0.51 gal |
| 2 in inside diameter, 100 ft | 16.32 gal |
| 4 in inside diameter, 50 ft | 32.64 gal |
| 25 mm inside diameter, 30 m | 14.726 L |
| 110 mm inside diameter, 10 m | 95.033 L |
Where the numbers come from
The fixed figures this calculator relies on, and the published source each one was checked against. How the calculators are built and checked
1 source
NIST Chemistry WebBook, water at 4 °C and 0.101325 MPa: 999.9749 kg/m³ (IAPWS-95), https://webbook.nist.gov/cgi/fluid.cgi?ID=C7732185, rounded to the conventional 1000 kg/m³ of NIST SP 811 (2008) Appendix B, centimeter of water, conventional = 98.0665 Pa.
Used for
- The conventional density of water, 1000 kg/m³. Pure water at 4 °C, its densest, is 999.97 kg/m³.
Common questions about the Pipe Volume Calculator
- How many gallons are in 100 feet of 1-inch pipe?
- With an inside diameter of exactly 1 inch, about 4.08 gallons: π × 0.5² × 1,200 inches is 942 cubic inches, and a US gallon is 231 cubic inches. Real 1-inch pipe is seldom exactly 1 inch inside, which is why the page asks for the inside diameter.
- Why not just pick the pipe size?
- Because the nominal size on the pipe is a name, not a measurement. Pipes of the same nominal size have different inside diameters depending on the material and the wall thickness, and volume goes with the square of the diameter, so a small difference in bore is a bigger one in gallons. Measure the bore or read it from the maker’s data.
- How much water is in each foot of pipe?
- Enter a length of 1 foot, or 1 metre, and read the volume. For a bore of exactly 1 inch it is about 0.041 gallons a foot; doubling the bore to 2 inches holds four times as much.
- What is the weight used for?
- It is the water inside the pipe, at 1,000 kilograms per cubic metre, useful when planning supports or when draining a line into a container. It does not include the pipe itself.