Concrete Pipe Volume Calculator
Same volume in every unit
Fluid weight
Estimated fill / drain time
Your recent calculations (saved on this device)
| When | ID | Length | Result |
|---|
For RCP the nominal size is the inside diameter, so the bore is loaded exactly as the size.
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.
RCP nominal size = inside diameter
Unlike steel or plastic pressure pipe, reinforced concrete pipe (RCP) is specified by its inside diameter. A 24-inch RCP has a 24-inch bore — the wall is added outside that. That makes the volume calculation refreshingly direct: pick the size, and the bore is the size. The wall thickness only matters if you are estimating the concrete in the pipe wall, which is a different calculation from the internal capacity this tool reports.
What concrete-pipe volume is used for
- Storm and culvert capacity — internal volume for detention and flow estimates.
- Line abandonment and grouting — the internal volume is the neat grout quantity.
- Cleaning and jetting — knowing contents helps plan water use and flushing.
- Detention and storage lines — large RCP is sometimes used as buried storage.
A culvert example in cubic yards
A 100 ft run of 36-inch RCP has a 3-foot bore, so the area is 7.07 ft² and the internal volume is about 707 ft³ — roughly 26.2 cubic yards or 5,290 US gallons. If you were grouting that line to abandon it, the cubic-yards figure is your starting grout order (before adding an allowance for losses). The calculator shows all of these units together.
Part-full gravity flow
Storm and sanitary RCP usually runs part full, not pressurised. If you want the water actually in the pipe at a given depth rather than the full-bore capacity, set a fill level below 100%. For precise part-full hydraulics (which depend on flow depth, slope and roughness), treat the fill-level result as an approximation and use a dedicated open-channel method for design.
Accuracy notes for RCP
Because nominal size equals the bore, the internal-volume result is exact for a full round pipe. The usual caveats apply for grouting (add a placement allowance) and for gravity flow (use the fill setting). For elliptical or arch pipe, the round-pipe model does not apply — use the manufacturer's cross-section.
Reading and trusting your result
The result above answers most questions; this note covers how to interpret it and its limits.
What the number actually means
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.
Water a 24" RCP holds by length
For reinforced concrete pipe the nominal size is the inside diameter, which keeps the arithmetic clean. A 24" RCP carries a lot — here is the standing volume as the run gets longer, in US gal.
| Length (ft) | Volume (US gal) | Per foot |
|---|---|---|
| 10 ft | 235 | 23.50 |
| 20 ft | 470 | 23.50 |
| 50 ft | 1,175 | 23.50 |
| 100 ft | 2,350 | 23.50 |
| 250 ft | 5,875 | 23.50 |
| 500 ft | 11,750 | 23.50 |
Capacity across RCP sizes
Because the bore equals the nominal size, volume climbs fast with diameter. Full-pipe contents for a 100 ft section across standard RCP sizes, in US gal:
| Nominal size | Bore (in) | Volume in 100 ft (US gal) |
|---|---|---|
| 12" | 12 | 588 |
| 18" | 18 | 1,322 |
| 24" | 24 | 2,350 |
| 36" | 36 | 5,288 |
| 48" | 48 | 9,400 |
A full-flow example
- Take a 36" RCP culvert, bore 36 in, radius 18 in.
- Area = π × 18² = 1,017.9 in².
- Over 40 ft (480 in) running full: 1,017.9 × 480 = 488,602 in³.
- That is 2,115 US gal in a 40 ft length — most storm pipe runs part-full, so scale by the fill depth for the real figure.
Frequently asked questions
How do I calculate concrete pipe volume?
For RCP the nominal size is the inside diameter, so just enter the size and length. The tool returns the internal capacity in cubic feet, cubic yards, gallons and m³.
Is the concrete pipe volume the internal space or the concrete itself?
This tool gives the internal (hollow) capacity — the water or air the pipe can hold. Estimating the concrete in the wall is a separate calculation using the wall thickness.
How much grout to fill an abandoned concrete pipe?
The internal volume is your neat grout quantity. Add a placement allowance (commonly 5–15%) for losses and over-break when ordering.
Can I get part-full volume for a storm line?
Set a fill level below 100% for an approximate part-full volume. For design-grade gravity flow, use an open-channel method that accounts for depth, slope and roughness.
Related pipe volume tools
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.