Pipe Volume Calculator
Find how much liquid a pipe holds. Choose a standard steel or PVC schedule, copper tube or PEX size, or type any inner diameter, add the length, and get the volume in US gallons, liters and cubic feet, the weight of the water and how long it takes to fill at your flow rate.
Last updated:
Density relative to water (water = 1).
Leave empty to skip the fill time.
How to use the Pipe Volume Calculator
- Choose how to size the pipe: a standard pipe or tube size, or a measured inner diameter.
- Pick the pipe type and nominal size (for example 2" Schedule 40 or 3/4" PEX), or type the inside diameter and its unit.
- Enter the length of the run in feet, meters or another unit.
- Select the fluid to get its weight, and optionally enter a flow rate for the fill time.
- Read the volume in gallons and liters, and compare other sizes in the table below.
Pipe volume formula
A full pipe is a cylinder, so its capacity depends only on the inside diameter and the length:
- Volume: V = π ÷ 4 × ID² × L
- US gallons = cubic inches ÷ 231; liters = cubic inches ÷ 61.024; cubic feet = cubic inches ÷ 1,728
- Shortcut: gallons per foot = 0.0408 × ID² (ID in inches); liters per meter = 0.000785 × ID² (ID in mm)
- Fluid weight = gallons × 8.34 lb × specific gravity
- Fill time = volume ÷ flow rate
Example: 100 ft of 2" Schedule 40 pipe has ID 2.067", so A = 0.7854 × 2.067² = 3.356 in², V = 3.356 × 1,200 in = 4,027 in³ = 17.4 US gal = 66.0 L, and the water weighs about 145 lb.
Steel and PVC pipe capacity (Schedule 40 and 80)
| NPS | Sch 40 ID (in) | Sch 40 gal/ft | Sch 40 gal/100 ft | Sch 80 ID (in) | Sch 80 gal/ft |
|---|---|---|---|---|---|
| 1/2" | 0.622 | 0.0158 | 1.6 | 0.546 | 0.0122 |
| 3/4" | 0.824 | 0.0277 | 2.8 | 0.742 | 0.0225 |
| 1" | 1.049 | 0.0449 | 4.5 | 0.957 | 0.0374 |
| 1-1/4" | 1.380 | 0.0777 | 7.8 | 1.278 | 0.0666 |
| 1-1/2" | 1.610 | 0.1058 | 10.6 | 1.500 | 0.0918 |
| 2" | 2.067 | 0.1743 | 17.4 | 1.939 | 0.1534 |
| 3" | 3.068 | 0.3840 | 38.4 | 2.900 | 0.3431 |
| 4" | 4.026 | 0.6613 | 66.1 | 3.826 | 0.5972 |
| 6" | 6.065 | 1.5008 | 150.1 | 5.761 | 1.3541 |
| 8" | 7.981 | 2.5988 | 259.9 | 7.625 | 2.3721 |
| 10" | 10.020 | 4.0963 | 409.6 | 9.562 | 3.7304 |
| 12" | 11.938 | 5.8146 | 581.5 | 11.374 | 5.2781 |
Dimensions follow ASME B36.10M (steel); Schedule 40 and 80 PVC to ASTM D1785 share the same outside diameters and wall thicknesses.
Copper tube and PEX capacity
| Copper size | Type K gal/ft | Type L gal/ft | Type M gal/ft |
|---|---|---|---|
| 3/8" | 0.0066 | 0.0075 | 0.0083 |
| 1/2" | 0.0113 | 0.0121 | 0.0132 |
| 3/4" | 0.0226 | 0.0251 | 0.0268 |
| 1" | 0.0404 | 0.0429 | 0.0454 |
| 1-1/4" | 0.0632 | 0.0653 | 0.0680 |
| 1-1/2" | 0.0895 | 0.0924 | 0.0951 |
| 2" | 0.1566 | 0.1608 | 0.1647 |
| 2-1/2" | 0.2419 | 0.2479 | 0.2540 |
| 3" | 0.3448 | 0.3539 | 0.3626 |
| 4" | 0.6070 | 0.6222 | 0.6317 |
| PEX size (SDR-9) | Approx. ID (in) | gal/ft | L/m |
|---|---|---|---|
| 3/8" | 0.360 | 0.0053 | 0.066 |
| 1/2" | 0.485 | 0.0096 | 0.119 |
| 3/4" | 0.681 | 0.0189 | 0.235 |
| 1" | 0.875 | 0.0312 | 0.388 |
| 1-1/4" | 1.069 | 0.0466 | 0.579 |
| 1-1/2" | 1.263 | 0.0651 | 0.808 |
| 2" | 1.653 | 0.1115 | 1.385 |
Copper tube is sized by ASTM B88 (outside diameter = nominal + 1/8"). PEX inside diameters here use the SDR-9 minimum wall from ASTM F876, so real tubing can hold slightly less. Always check the manufacturer's data when the exact volume matters, for example when dosing antifreeze or water treatment.
Tips
- Hydronic and solar loops: add the volume of the boiler, heat exchanger, expansion tank and fittings to the pipe volume before buying glycol.
- Hot water wait: the water already in the line must run out before hot water arrives. Volume ÷ faucet flow gives the delay.
- Flushing and disinfection: line volume tells you how much water one full flush uses and how much disinfectant is needed for a target concentration.
- Pipe supports: the water weight shown is for the liquid only. Add the weight of the empty pipe and insulation when spacing hangers.
Frequently asked questions
How do you calculate the volume of a pipe?
Use the inside diameter: V = π × (ID ÷ 2)² × length. With the diameter in inches and length in inches you get cubic inches; divide by 231 for US gallons or by 61.024 for liters. A handy shortcut is gallons per foot = 0.0408 × ID² (ID in inches).
How many gallons are in 100 feet of 2 inch pipe?
2" Schedule 40 steel or PVC has an inside diameter of 2.067", so it holds 0.0408 × 2.067² ≈ 0.174 gallons per foot, or about 17.4 US gallons (66 liters) per 100 feet. Schedule 80 (ID 1.939") holds about 15.3 gallons per 100 feet.
Why use the inside diameter and not the nominal size?
Nominal pipe size is only a name. A 1" Schedule 40 pipe is really 1.049" inside, 1" Schedule 80 is 0.957", 1" copper Type L is 1.025" and 1" PEX is about 0.875". The thicker the wall, the less liquid the pipe holds, so this calculator looks up the real inside diameter for each type.
How much does the water in a pipe weigh?
Fresh water weighs about 8.34 lb per US gallon (1 kg per liter). Multiply the volume in gallons by 8.34 and by the fluid's specific gravity for other liquids, for example about 1.025 for seawater or 0.85 for diesel. The result is the fluid only; add the empty pipe weight for supports.
How long does it take to fill a pipe?
Divide the volume by the flow rate. 100 feet of 2" Schedule 40 holds about 17.4 gallons, so at 10 GPM it fills in about 1.7 minutes. The same formula estimates how long a line takes to drain or how long before hot water reaches a faucet.
How many gallons per foot is 3/4 inch PEX or copper?
3/4" PEX (SDR-9) holds about 0.018 to 0.019 gallons per foot, 3/4" copper Type L about 0.025 gallons per foot, and 3/4" Schedule 40 pipe about 0.028 gallons per foot. That is why a long 3/4" PEX run can take noticeably longer to deliver hot water than you might expect from its size alone.
Does this work for gas or air in a pipe?
The geometric volume (cubic feet or liters) is the same for any fluid. For gases the mass depends strongly on pressure and temperature, so use the volume here together with the gas law rather than the liquid weight shown.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.