Pipe Volume Calculator
Use our pipe volume calculator to calculate the volume of water in a pipe from inner diameter and length (inches). Get pipe volume in gallons and estimated water weight in pounds. Includes the pipe volume formula and a quick volume of pipe chart.
What Is Pipe Volume?
Pipe volume is the amount of space inside a pipe that can hold water (or another fluid). For a straight, round pipe, the inside volume is the volume of a cylinder based on the inner diameter and length.
Knowing how many gallons are in a pipe helps with filling, draining, chemical dosing, flushing, and estimating system capacity.
This calculator uses inner diameter (in) and length (in) to return pipe volume (US gallons) and an estimated water weight (lb).
Pipe Volume Formula
For a round pipe, volume is cylinder volume. Then convert cubic inches to gallons and estimate water weight.
d is inner diameter (in) and L is length (in).
1 US gallon = 231 cubic inches.
8.34 lb/gal is a common approximation for water near room temperature.
Use inner diameter, not nominal pipe size, for best accuracy.
Volume of Pipe Chart
Quick gallons-per-foot reference for common inner diameters (rounded).
| Inner diameter (in) | Gallons per foot |
|---|---|
| 0.5 | 0.0102 |
| 0.75 | 0.0230 |
| 1 | 0.0408 |
| 1.5 | 0.0918 |
| 2 | 0.1632 |
| 3 | 0.3672 |
| 4 | 0.6528 |
| 6 | 1.4688 |
How to Calculate Pipe Volume
- 1
Enter the inner diameter of the pipe (in).
- 2
Enter the pipe length (in).
- 3
The calculator finds cylinder volume in cubic inches: π × (d/2)² × L.
- 4
It converts cubic inches to gallons by dividing by 231.
Frequently Asked Questions
Treat the pipe as a cylinder: V = π × (d/2)² × L. Then convert cubic inches to gallons by dividing by 231.
This calculator uses the pipe’s inner diameter and length. The result is the internal volume in US gallons.
Convert feet to inches first (in = ft × 12), then run the calculation using inches.
It calculates capacity (volume) and water weight from a known inner diameter and length. Choosing pipe size for flow/pressure requires additional info like flow rate, velocity, friction losses, and material.
Yes. Compute V = PI()*(d/2)^2*L, then gallons = V/231, then weight = gallons*8.34.