Pipe Volume Calculator
Work out how much water a pipe or a run of pipes holds in gallons and liters, from its size or inside diameter and length. Add a run per size of steel, PVC, copper or PEX, or type any inside diameter, and see the water weight, the fill time at a given flow and the dose for a target concentration.
Your numbers
Pipe runs
Up to 8 runs, one per size and material. Add the lengths of each size together.
Optional
To see how long the line takes to fill or to flush one volume.
From the job's specification or the water authority, e.g. for disinfecting a new line.
The available chlorine (or active ingredient) on the label.
Water in the pipe
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- Liters
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- Cubic feet
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- Cubic meters
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- Weight of the water
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The calculation runs in your browser and ParrotNotes does not store your numbers. They sit in the page address so you can bookmark or share the result.
How to calculate pipe volume
A pipe is a long cylinder, so its volume is the inside cross-section times the length: π ÷ 4 × inside diameter² × length. Work in inches and feet, multiply the feet by 12 to get inches, and divide the cubic inches by 231 to get US gallons. The calculator also shows liters, cubic feet and cubic meters.
Worked example: 100 ft of 2 in Schedule 40 steel pipe, 2.067 in inside. π ÷ 4 × 2.067² × 100 × 12 ÷ 231 = 17.43 gallons, which is 65.99 liters, and the water weighs 17.43 × 8.34 = 145.4 lb. For a line that changes size, add a run per size: 120 ft of 3/4 in Type L copper (3.02 gal) plus 40 ft of 1 in Type L (1.71 gal) holds 4.73 gallons.
Gallons per foot by pipe size
Gallons per foot for every preset in the calculator. Multiply by the length in feet for the volume of a run. Blank cells are sizes the table for that material does not list.
| Size | Steel, Schedule 40 | Steel, Schedule 80 | PVC, Schedule 40 | PVC, Schedule 80 | Copper, Type K | Copper, Type L | Copper, Type M | PEX (SDR 9) |
|---|---|---|---|---|---|---|---|---|
| 1/2 in | 0.0158 | 0.0122 | 0.0148 | 0.0113 | 0.0113 | 0.0121 | 0.0132 | 0.0096 |
| 3/4 in | 0.0277 | 0.0225 | 0.0264 | 0.0213 | 0.0226 | 0.0251 | 0.0268 | 0.0189 |
| 1 in | 0.0449 | 0.0374 | 0.0432 | 0.0357 | 0.0404 | 0.0429 | 0.0454 | 0.0312 |
| 1 1/4 in | 0.0777 | 0.0666 | 0.0755 | 0.0642 | 0.0632 | 0.0653 | 0.068 | 0.0466 |
| 1 1/2 in | 0.1058 | 0.0918 | 0.1031 | 0.0889 | 0.0895 | 0.0924 | 0.0951 | 0.0651 |
| 2 in | 0.1743 | 0.1534 | 0.171 | 0.1493 | 0.1566 | 0.1608 | 0.1647 | 0.1115 |
| 2 1/2 in | 0.2487 | 0.2202 | 0.2439 | 0.2138 | 0.2419 | 0.2479 | 0.254 | |
| 3 in | 0.384 | 0.3431 | 0.3776 | 0.3347 | 0.3448 | 0.3539 | 0.3626 | |
| 3 1/2 in | 0.4675 | 0.4786 | 0.4882 | |||||
| 4 in | 0.6613 | 0.5972 | 0.6521 | 0.5848 | 0.607 | 0.6196 | 0.6318 | |
| 6 in | 1.5008 | 1.3541 | 1.484 | 1.3298 |
Inside diameters by material
Steel pipe uses the ASME B36.10 inside diameters for Schedule 40 and 80, as tabled by Engineering ToolBox; the Schedule 40 figures are the ones the flow rate calculator uses. PVC pipe uses the average inside diameters on Rain Bird's Schedule 40 and Schedule 80 pipe charts, which match the ASTM D1785 table of the PVC maker Harrison Machine & Plastic.
Copper Types K, L and M (ASTM B88) share an outside diameter per size and differ by wall; the inside diameter here is the outside diameter minus two walls, from Engineering ToolBox's B88 table, and Rain Bird's Type K chart gives the same figures. PEX is ASTM F876 SDR 9 tube: outside diameter minus two minimum walls, the largest bore the standard allows. Walls run a little over the minimum, so a brand's tube can hold slightly less; type its inside diameter if the maker gives one.
Water weight, fill time and dosing
Weight uses 8.34 lb per gallon and 1 kg per liter, from the California Water Boards' distribution operator formula sheet. Add a flow in GPM and the calculator gives the time to fill the line, or to push one line volume through it when flushing: minutes = gallons ÷ GPM. A 1,000 ft run of 6 in Schedule 40 PVC holds 1,484 gallons; at 100 GPM that is 14.8 minutes.
For a chemical dose, type the target concentration and the product's strength. The same sheet gives pounds = million gallons × mg/L × 8.34 ÷ (strength ÷ 100). For example, 1,484 gallons with 50 mg/L typed and a 65% product gives 0.95 lb (432 g). The calculator does not suggest a concentration: it comes from the job's specification or the water authority, along with the contact time, flushing and testing.
What this calculator does not count
Fittings, valves, meters, tanks, water heaters and anything else on the line are not in the volume, and a partly full pipe is not modelled. For a tank, the tank volume calculator works out round, rectangular and capsule tanks; for how fast the water moves or how much pressure a column of water gives, use the flow rate calculator.
For plumbers, irrigation reps and water operators
A flush, a disinfection or a drain-down quote starts from what is in the ground and the walls: the sizes, the run lengths, the material and what the customer or the operator says about the old line. Those come up on the walk-through, and the one that gets missed is the one that changes the price.
Sources, each read on 2026-10-26. All results are estimates for checking and quoting:
- NIST Handbook 44, Appendix C: General Tables of Units of Measurement (1 gallon = 231 cubic inches)
- California Water Boards: distribution operator formula sheet (8.34 lb per gallon, fill time, chlorine pounds)
- Engineering ToolBox: ASME/ANSI B36.10 steel pipe dimensions (Schedule 40 and 80 inside diameters)
- Rain Bird: PVC Schedule 40 IPS plastic pipe chart (average inside diameters)
- Rain Bird: PVC Schedule 80 IPS plastic pipe chart (average inside diameters)
- Harrison Machine & Plastic: Schedule 40 and 80 PVC pipe specifications, ASTM D1785 (copy on InspectAPedia)
- Engineering ToolBox: ASTM B88 seamless copper water tube, Types K, L and M (outside diameter and wall)
- Rain Bird: Type K copper water tube chart (inside diameters)
- Engineering ToolBox: ASTM F876 PEX tube, SDR 9 (outside diameter and minimum wall)
- AWWA C651, Disinfecting Water Mains (standard listing; the text is sold by AWWA and was not read for this page)
Working out a tank as well? Use the tank volume calculator for it, and for GPM, velocity and head pressure the flow rate calculator.
More for trades and home services sales: Home improvement sales, Quote follow-up email.
The run lengths come up on the walk-through
So do the pipe sizes, the material and what the customer says about the old line. Record the visit in ParrotNotes and get a structured note, a summary and the action items, so the flush, the dose and the quote start from the same numbers. Free for 100 minutes of recording a month.
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