Pipe Volume Calculator — Barrels (bbl)
Same volume in every unit
Fluid weight
Estimated fill / drain time
Your recent calculations (saved on this device)
| When | ID | Length | Result |
|---|
One barrel here is the 42-US-gallon oil barrel. The gallons card is shown for cross-checking.
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.
Which barrel — and why it matters
The barrel used across the petroleum industry is the US oil barrel of exactly 42 US gallons (158.99 litres). It is not the same as a fluid barrel, a beer barrel or a dry barrel, so mixing them up is a costly slip. This tool uses the 42-gallon oil barrel throughout and shows US gallons alongside so you can always verify the figure.
Barrels from bore and length
Compute the volume in gallons or cubic feet first, then convert:
- US gallons ÷ 42 = oil barrels.
- Cubic feet × 0.17811 = oil barrels.
- Cubic metres × 6.2898 = oil barrels.
For example, 1,000 ft of 6-inch line (bore 6.065 in) holds about 1,499 US gallons, or roughly 35.7 barrels. Multiply by the number of parallel runs, or set a length in miles by entering feet, to scale up to gathering-line lengths.
Capacity, displacement and pump strokes
Two related quantities matter in the field. Capacity is the internal volume the tool returns. Displacement is what a string pushes aside — for open-ended pipe that is the metal cross-section, and for the annulus it is capacity minus the volume of anything inside. For fill, flush and pump-stroke planning, start from the barrels-per-foot capacity here and adjust for the string or tool geometry in your own procedure.
Where barrels are used
Pipeline batching and interface tracking, line fill before hydrotest, pigging and flushing volumes, tank-to-line reconciliation and spill estimation all lean on an accurate barrels figure. The same per-foot value scales cleanly from a short jumper to miles of gathering line.
Keeping the barrels figure honest
Use the true internal diameter for the pipe grade and schedule you actually have, not the nominal size, and remember that scale, liner or wax reduces the effective bore over time. For annular volumes, subtract the enclosed string. With the correct bore in place, the barrels result is a solid basis for field procedures.
Reading and trusting your result
A volume figure is only useful if you know what it assumes — so a quick word on reading your pipe volume calculator barrels result.
How to interpret the result
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 barrels. The per-foot figure is constant, so any length is one multiplication away.
| Length (ft) | Volume (barrels) | Per foot |
|---|---|---|
| 10 ft | 0.0415 | 0.0042 |
| 25 ft | 0.1038 | 0.0042 |
| 50 ft | 0.2075 | 0.0042 |
| 100 ft | 0.4150 | 0.0042 |
| 250 ft | 1.04 | 0.0042 |
| 500 ft | 2.08 | 0.0042 |
Schedule 40 pipe: volume across sizes
Volume held by a fixed 100 ft run across common Schedule 40 sizes, in barrels. Doubling the diameter roughly quadruples the capacity.
| Nominal size | Bore (in) | Volume in 100 ft (barrels) |
|---|---|---|
| 1/2" | 0.622 | 0.0376 |
| 3/4" | 0.824 | 0.0660 |
| 1" | 1.049 | 0.1069 |
| 1-1/2" | 1.610 | 0.2518 |
| 2" | 2.067 | 0.4150 |
| 3" | 3.068 | 0.9144 |
| 4" | 4.026 | 1.57 |
| 6" | 6.065 | 3.57 |
Worked example, step by step
- Bore = 2.067 in, so radius = 1.0335 in.
- Area = π × radius² = 3.3556 in².
- Length = 75 ft = 900 in; volume = 3.3556 × 900 = 3,020.0 in³.
- Convert to the unit you need: 0.3113 barrels for a 75 ft run of Schedule 40 2" pipe.
Frequently asked questions
How many barrels of oil fit in a pipe?
Divide the pipe's US-gallon capacity by 42. The calculator shows barrels and gallons together so you can check the conversion at a glance.
What is barrels per foot for common line sizes?
It scales with the bore squared. A foot of 4-inch Schedule 40 holds about 0.0158 bbl; a foot of 6-inch about 0.0357 bbl. Enter your exact size above for the precise value.
Is a barrel 42 gallons or 55 gallons?
The oil barrel is 42 US gallons. The 55-gallon figure refers to a common steel drum, which is a container size, not the petroleum barrel used for line volume.
What is the difference between pipe capacity and displacement?
Capacity is the fluid a pipe can hold inside. Displacement is the volume the pipe wall or a run-in string pushes aside. This tool gives capacity; adjust for displacement in your procedure.
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What people say
The fill-time estimate turned a vague flush task into a scheduled one. Handy.
Clear about its own limits — tells you when to check manufacturer data. Trustworthy.
Clean and quick on my phone in the field.