# What is the pipe volume?

Works out how much water a pipe holds from its inner diameter (or outer diameter and wall) and length, in gallons, liters, cubic feet and cubic meters, with the weight of the water.

- Page: https://www.acalculator.org/construction/pipe-volume-calculator
- JSON spec: https://www.acalculator.org/construction/pipe-volume-calculator.json
- Version: c1e61401e63d

## Default answer

Example with the default inputs (I know the Inner diameter, Inner diameter 2 in, Pipe length 100 ft, Number of pipes 1): The pipes hold 16.32 US gallons (136.1 lb of water): 1 × 100 ft with an inside of 2 in.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| given | I know the | The inner diameter, or the outer diameter and the wall thickness. |
| id | Inner diameter | The distance across the inside of the pipe. |
| od | Outer diameter | The distance across the outside of the pipe. |
| wall | Wall thickness | The thickness of the pipe wall. |
| length | Pipe length | The length of one pipe. |
| n | Number of pipes | How many pipes of this size and length. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| gallons | US gallons | The water the pipes hold, in US gallons of 231 in³. |
| liters | Liters | The water the pipes hold, in liters. |
| cubicFeet | Cubic feet | The inside volume in cubic feet. |
| cubicMeters | Cubic meters | The inside volume in cubic meters. |
| pounds | Water weight (lb) | The weight of the water at 60 °F, in pounds. |
| kilograms | Water weight (kg) | The weight of the water at 60 °F (15.6 °C), in kilograms. |
| perFoot | Gallons per foot | The water one foot of this pipe holds. |
| perMeter | Liters per meter | The water one meter of this pipe holds. |
| inner | Inner diameter (in) | The inside diameter used, in inches. |
| innerMm | Inner diameter (mm) | The inside diameter used, in millimeters. |

## Method

V = π × (d ÷ 2)² × L × n, with d the inner diameter (or outer diameter − 2 × wall); water weight = V × 999.07 kg/m³.

## Assumptions

- The pipe is a straight round tube, full of water. Fittings, bends and valves are not counted.
- Water weighs 0.99907 g/cm³ (62.366 lb/ft³) at 60 °F (15.6 °C); warmer water weighs a little less.
- 1 US gallon is 231 in³ (3.785411784 L).

## Worked examples

1. given = inner, id = 0.0508, length = 30.48, n = 1 gives gallons = 16.319962, perFoot = 0.1632, cubicFeet = 2.181662. Source: OpenStax, Prealgebra 2e, §9.6 Solve Geometry Applications: Volume and Surface Area (V = πr²h). https://openstax.org/books/prealgebra-2e/pages/9-6-solve-geometry-applications-volume-and-surface-area; NIST Handbook 44, Appendix C, General Tables of Units of Measurement (1 in = 2.54 cm; 1 US gallon = 231 in³; 1 lb = 0.45359237 kg). https://www.nist.gov/pml/owm/nist-handbook-44-current-edition.
2. given = inner, id = 0.1, length = 10, n = 3 gives cubicMeters = 0.235619, liters = 235.619449, kilograms = 235.400323. Source: OpenStax, Prealgebra 2e, §9.6 Solve Geometry Applications: Volume and Surface Area (V = πr²h). https://openstax.org/books/prealgebra-2e/pages/9-6-solve-geometry-applications-volume-and-surface-area; USGS Water Science School, Water Density (0.99907 g/cm³ at 60 °F). https://www.usgs.gov/special-topics/water-science-school/science/water-density.
3. given = outer, od = 0.060325, wall = 0.003912, length = 3.048, n = 1 gives inner = 2.067, gallons = 1.743171. Source: OpenStax, Prealgebra 2e, §9.6 Solve Geometry Applications: Volume and Surface Area (V = πr²h). https://openstax.org/books/prealgebra-2e/pages/9-6-solve-geometry-applications-volume-and-surface-area; NIST Handbook 44, Appendix C, General Tables of Units of Measurement (1 in = 2.54 cm; 1 US gallon = 231 in³; 1 lb = 0.45359237 kg). https://www.nist.gov/pml/owm/nist-handbook-44-current-edition.

## FAQ

### How do I calculate the volume of a pipe?

A pipe’s inside is a cylinder: V = π × (d ÷ 2)² × L, with d the inside diameter and L the length. 100 ft of pipe 2 in across inside holds π × 1² × 1,200 = 3,769.9 in³, which is 3,769.9 ÷ 231 = 16.32 US gallons.

### Should I use the inside or the outside diameter?

The inside diameter, because only the inside holds water. If you know the outside diameter and the wall thickness, the inside is the outside minus two walls. A pipe 2.375 in across outside with a 0.154 in wall is 2.067 in across inside.

### How many gallons are in one foot of pipe?

One foot of pipe holds π × (d ÷ 2)² × 12 ÷ 231 gallons, with d in inches. That is 0.1632 gallons for a 2 in inside diameter and 0.0408 gallons for 1 in.

### How much does the water in a pipe weigh?

Multiply the volume by the density of water. At 60 °F water is 0.99907 g/cm³, or 62.366 lb per cubic foot, so 16.32 gallons (2.18 ft³) weighs about 136 lb.

### Does the length unit matter?

No. Type the length in feet, inches, yards, miles, meters, centimeters or kilometers, and the diameters in inches, feet, millimeters, centimeters or meters. The page converts them before it multiplies.

### Are fittings and bends counted?

No. The page treats the pipe as one straight tube. Elbows, tees and valves hold a little more; add their length if you know it.

## Sources

- OpenStax, Prealgebra 2e, §9.6 Solve Geometry Applications: Volume and Surface Area (V = πr²h for a cylinder). https://openstax.org/books/prealgebra-2e/pages/9-6-solve-geometry-applications-volume-and-surface-area (retrieved 2026-10-02)
- NIST Handbook 44, Appendix C, General Tables of Units of Measurement (1 in = 2.54 cm; 1 US gallon = 231 in³ = 3.785411784 L; 1 lb = 0.45359237 kg). https://www.nist.gov/pml/owm/nist-handbook-44-current-edition (retrieved 2026-10-02)
- USGS Water Science School, Water Density (0.99907 g/cm³ and 62.366 lb/ft³ at 60 °F, 15.6 °C). https://www.usgs.gov/special-topics/water-science-school/science/water-density (retrieved 2026-10-02)