Pipe volume calculator
How many gallons a pipe, well casing or hose holds, from its inside diameter and length, with gallons per foot and time to fill.
The pipe holds
4.08 gallons
- Liters
- 15.44 L
- Cubic feet
- 0.545 cu ft
- Gallons per foot (average)
- 0.0408 gal/ft
- Total length
- 100.0 ft
- Time to fill or flush
US gallons. Use the pipe's inside diameter: a pipe's nominal size isn't its inside diameter, which depends on the material and wall thickness.
How to calculate pipe volume
A pipe is a cylinder, so its volume is the area of the inside circle times the length. Work in inches, then convert to gallons: a US gallon is 231 cubic inches.
- Area = 3.1416 × (inside diameter ÷ 2)², in square inches
- Cubic inches = area × length in feet × 12
- Gallons = cubic inches ÷ 231
- Shortcut: gallons per foot = inside diameter² × 0.0408
Worked example
A house with 100 ft of 3/4 in pipe and 60 ft of 1/2 in pipe (inside diameters): 0.75² × 0.0408 × 100 = 2.29 gal, and 0.50² × 0.0408 × 60 = 0.61 gal. Together the lines hold 2.91 gallons.
Gallons per foot of pipe chart
By inside diameter. Check your pipe's actual inside diameter with the maker's spec; for the same nominal size, thicker walls hold less.
| Inside diameter | Gallons per foot | Gallons per 100 ft | Liters per foot |
|---|---|---|---|
| 1/2 in | 0.0102 | 1.0 | 0.039 |
| 3/4 in | 0.0229 | 2.3 | 0.087 |
| 1 in | 0.0408 | 4.1 | 0.154 |
| 1 1/4 in | 0.0637 | 6.4 | 0.241 |
| 1 1/2 in | 0.0918 | 9.2 | 0.347 |
| 2 in | 0.1632 | 16.3 | 0.618 |
| 2 1/2 in | 0.2550 | 25.5 | 0.965 |
| 3 in | 0.3672 | 36.7 | 1.390 |
| 4 in | 0.6528 | 65.3 | 2.471 |
| 5 in | 1.0200 | 102.0 | 3.861 |
| 6 in | 1.4688 | 146.9 | 5.560 |
| 8 in | 2.6112 | 261.1 | 9.884 |
| 10 in | 4.0800 | 408.0 | 15.444 |
| 12 in | 5.8752 | 587.5 | 22.240 |
Pipe volume questions
What is the formula for pipe volume?
Volume = 3.1416 × radius² × length, with the radius being half the inside diameter. In inches and feet, gallons = 3.1416 × (diameter ÷ 2)² × length × 12 ÷ 231, which works out to diameter² × 0.0408 gallons per foot.
How many gallons per foot are in a 6 inch pipe?
1.47 gallons per foot for a 6 in. inside diameter, or 147 gallons per 100 ft. A 4 in. inside diameter holds 0.653 gallons per foot and a 2 in. holds 0.163. The chart above covers ½ in. to 12 in.
Is a pipe's size its inside diameter?
Not exactly. Pipe is sold by a nominal size, and the inside diameter depends on the material and wall thickness: schedule 40 and schedule 80 pipe of the same nominal size have different insides, and copper and PEX tubing differ again. For a close answer, measure the inside or look up the maker's dimensions, and enter that diameter.
How much water is in my house's pipes?
Usually only a few gallons. A house with 100 ft of 3/4 in and 60 ft of 1/2 in supply lines holds about 2.9 gallons. Set "Pipe sizes to add up" to the number of sizes you have and enter each one's length.
How long does it take to fill or flush a pipe?
Divide the gallons by the flow in gallons per minute. Enter your flow rate above, from the pump or fixture spec or by timing how long it takes to fill a bucket, and the calculator shows the time. Flushing a well or a line usually takes several times the pipe's volume, so follow the instructions for the job.
Can I use this for a tank or a pool?
A round tank lying on its side is a cylinder too, so enter its inside diameter (in inches) and length. For pools, use the pool volume calculator; for boxes and other shapes, the cubic feet calculator.