Pipe Volume Calculator — Cubic Metres (m³)
Same volume in every unit
Fluid weight
Estimated fill / drain time
Your recent calculations (saved on this device)
| When | ID | Length | Result |
|---|
Cubic metres is the default. For smaller pipes the litres card is usually easier to read.
How to use this calculator
- Choose the unit system — US, Imperial or metric — at the top of the calculator.
- Pick the pipe type and schedule, then the nominal size, and the real inside diameter loads for you. Or choose Custom and type any bore.
- Enter the pipe length. Open Advanced to set fill level, number of identical runs, a fittings allowance, the fluid, or a flow rate.
- Press Calculate to see the volume in every unit, plus fluid weight, cross-section area and fill or drain time.
- Copy, share or print the result. Recent calculations are saved on your own device so you can reopen them later.
Tip: not sure where to start? Use the Fill example data button to load a complete worked example — a 2-inch Schedule 40 line, 50 ft long, at 10 gal/min — then adjust the numbers to match your job.
Real-world uses, with numbers
Charging a radiant-heat loop
How much water sits in a 300 ft run of ½" PEX.
≈ 2.9 US galSizing a well pressure tank
Line-fill volume in 100 ft of 1" Schedule 40.
≈ 4.5 US galFlushing a main
Water to displace in 100 ft of 4" Schedule 40.
≈ 66 gal · 250 LWater weight on hangers
Load from a full 100 ft run of 2" pipe.
≈ 145 lb · 66 kgMetric heating fill
Charge volume for 50 m of 28 mm bore.
≈ 30.8 LFuel or oil line contents
Diesel held in 20 m of 50 mm bore.
≈ 39 L · 33 kgMore questions, answered
How do I convert between gallons, litres and cubic metres?
1 US gallon = 3.785 litres; 1 Imperial gallon = 4.546 litres; 1 m³ = 1,000 litres = 264.2 US gallons. The calculator shows all of them from a single entry, so you never convert by hand.
Does the pipe material change the volume?
Only through the bore. Two pipes with the same inside diameter hold the same volume whether they are steel, PVC, copper or PEX. Material and schedule matter because they set the real inside diameter for a given nominal size.
How much does the water inside a pipe weigh?
About 8.34 lb per US gallon, or 1 kg per litre. A full 100 ft run of 2" Schedule 40 holds roughly 17.4 gallons, about 145 lb. Set the fluid in Advanced for hot water, glycol, diesel or seawater.
What if I only know the outside diameter?
Switch the diameter to OD mode and enter the wall thickness; the tool subtracts two wall thicknesses to reach the bore. For a listed standard, just pick the size and the published inside diameter loads automatically.
Can I use it for a part-full or sloped drain?
Yes for a straight, round pipe: open Advanced and set the fill level below 100%, and the volume scales with it. Truly partial gravity flow in a sloped line follows a curved free surface, so treat the part-full figure as an approximation.
Notes and derived figures
- Volume scales with the square of the bore: doubling the inside diameter roughly quadruples the capacity, while doubling the length only doubles it.
- Per-foot and per-metre capacity are constant for a given bore, so any length is a single multiplication — handy for quick field estimates.
- Nominal size is a label. A "2-inch" Schedule 40 pipe has a 2.067-inch bore; using "2" overstates the volume by more than a third.
- Fill and drain time is volume divided by flow rate. Enter a flow rate in Advanced to turn any result into a charge, flush or drain time.
Cubic metres, the SI volume
One cubic metre is 1,000 litres — a large unit that suits mains, culverts and bulk lines but leaves small pipes reading as tiny decimals. The calculator shows litres in the same panel so you can pick whichever scale is comfortable. The core relationship is:
m³ = π × (IDm / 2)² × Lm
A mains-scale example
Consider 500 m of DN300 (12-inch) pipe with a 300 mm bore. Area = π × (0.15)² = 0.0707 m²; volume = 0.0707 × 500 = 35.3 m³, or 35,300 litres. That single figure drives disinfection dosing, fill time and the water a section loses when it is taken out of service — all of which the tool can estimate from the same inputs.
Cubic metres conversions
- 1 m³ = 1,000 litres = 264.17 US gallons = 219.97 Imperial gallons.
- 1 m³ = 35.315 cubic feet = 1.308 cubic yards.
- 1 m³ of water ≈ 1,000 kg (one tonne).
Where cubic metres matters
Municipal and industrial water networks plan disinfection and flushing by the cubic metre. Civil projects reconcile pipe contents against tanker and storage volumes in m³. Process plants log line inventory in m³ for mass balances. In each case the internal volume is the starting point, and the tonne of water inside a large main is a load worth knowing before a section is drained or filled.
Getting an accurate m³ figure
Two things keep large-line estimates honest. First, use the real bore — for plastic mains that means the OD and the SDR/DR, not the nominal size. Second, decide whether the line is truly full: gravity sewers and part-charged mains should use the fill-level setting. With those in place the cubic-metre figure is a dependable planning number.
Reading and trusting your result
Here is how to read the number this pipe volume calculator in m3 gives you, and where it stops being exact.
What the figure represents
The headline value is the internal capacity of a round, uniform pipe running full — the fluid the bore can hold along the length you entered. Every other unit on the panel is the same physical quantity re-expressed, so you can quote whichever your paperwork needs without recalculating.
The full-pipe assumption
By default the figure assumes the pipe is completely full and perfectly cylindrical. For gravity drains and vented lines that run part full, set a fill level below 100% and the result scales with it. Bends, valves and fittings add a little capacity the straight-length model does not see — use the fittings allowance to approximate them.
Capacity reference tables & a worked example
Concrete numbers for this page, calculated the same way the tool above does — use them as a quick check or a lookup.
Schedule 40 2" pipe: volume by run length
How much a 2" Schedule 40 bore holds as the run gets longer, in m³. Multiply or interpolate for your exact length.
| Length (m) | Volume (m³) | Per metre |
|---|---|---|
| 3 m | 0.0065 | 0.0022 |
| 8 m | 0.0173 | 0.0022 |
| 15 m | 0.0325 | 0.0022 |
| 30 m | 0.0649 | 0.0022 |
| 75 m | 0.1624 | 0.0022 |
| 150 m | 0.3247 | 0.0022 |
Schedule 40 pipe: volume across sizes
Volume held by a fixed 30 m run across common Schedule 40 sizes, in m³. Because the bore is squared, capacity climbs fast with size.
| Nominal size | Bore (in) | Volume in 30 m (m³) |
|---|---|---|
| 1/2" | 0.622 | 0.0059 |
| 3/4" | 0.824 | 0.0103 |
| 1" | 1.049 | 0.0167 |
| 1-1/2" | 1.610 | 0.0394 |
| 2" | 2.067 | 0.0649 |
| 3" | 3.068 | 0.1431 |
| 4" | 4.026 | 0.2464 |
| 6" | 6.065 | 0.5592 |
Worked example, step by step
- Bore = 2.067 in = 0.0525 m, so radius = 0.02625 m.
- Area = π × radius² = 0.002165 m².
- Volume = area × length = 0.002165 × 25 = 0.05412 m³.
- Convert: 0.05412 m³ = 0.0541 m³ for a 25 m run.
Frequently asked questions
How do I calculate pipe volume in cubic metres?
Work in metres throughout: area = π × (bore/2)², then multiply by length. The calculator converts mm and any length unit to m³ for you.
How many litres in a cubic metre of pipe?
Exactly 1,000 litres per cubic metre. The result shows both so you can read whichever suits the pipe size.
How much does a cubic metre of water in a pipe weigh?
About 1,000 kg, or one tonne. The weight card shows the exact figure for your chosen fluid.
Should I use nominal size for a large plastic main?
No — use the outside diameter with the SDR or DR, which the HDPE option handles. Nominal size overstates the bore and therefore the m³.
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What people say
Used the litres-per-metre figures to size a glycol charge for a radiant job. Numbers matched the datasheet.
Switches between US and metric without losing the pipe. Small thing, big time-saver.
Would love more HDPE DIPS sizes, otherwise excellent.