1 in schedule 40 pipe flow and volume calculator
1 in schedule 40 pipe has an outside diameter of 33.4 mm and a bore of 26.6 mm, a wall thickness of 3.40 mm. Nominal pipe size is a label, not a measurement — nothing about a 1-inch pipe is one inch.
Domestic water is usually kept between 1 and 2.4 m/s to limit noise and erosion.
Copper and plastic about 140; new steel 130; old steel 100.
- Flow in US gallons per minute
- 13.212
- Inside diameter
- 26.60
- Wall thickness
- 3.400
- Bore area
- 555.72 mm2
- Water content per metre
- 0.5557
- Water in the run
- 13.89
- Weight of that water
- 13.89
- Friction head loss
- 2.630
- Pressure drop
- 25.788 kPa
Show the working
- Flow velocity = 1.5
- Pipe run = 25
- Hazen-Williams C = 140
- Fluid density = 1000
- Inside diameter = 26.6 = 26.6
- outside = 33.4 = 33.4
- Wall thickness = (33.4 - 26.6) / 2 = 3.4
- Bore area = pi * 26.6^2 / 4 = 555.716
- area_m2 = 555.716 / 1e6 = 0.000 555 716
- Water content per metre = 555.716 / 1000 = 0.555 716
- Water in the run = 0.555 716 * 25 = 13.8929
- flow_m3s = 0.000 555 716 * 1.5 = 0.000 833 574
- Flow at that velocity = 0.000 833 574 * 60000 = 50.0145
- Flow in US gallons per minute = 50.0145 / 3.785411784 = 13.2124
- loss_per_m = 10.67 * (0.000 833 574)^1.852 / (140^1.852 * (26.6/1000)^4.87) = 0.105 184
- Friction head loss = 0.105 184 * 25 = 2.629 61
- Pressure drop = 2.629 61 * 1000 * g0 / 1000 = 25.7876
- Weight of that water = 13.8929 * 1000 / 1000 = 13.8929
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
Scenarios & local history
Compare a saved scenario
Recent calculations
The formula
- bore area = pi d^2 / 4
- flow = area x velocity
- Hazen-Williams head loss per metre = 10.67 Q^1.852 / (C^1.852 d^4.87), SI units
Nominal pipe size is a legacy label. Above 14 inch NPS the outside diameter equals the nominal size; below it, neither dimension matches.
Hazen-Williams is an empirical formula fitted to water near room temperature. For other fluids or for gases, use Darcy-Weisbach.
Fittings add loss too. A rule of thumb is to add 30 to 50% to the straight-run figure for a typical domestic circuit.
1 in pipe at common velocities
| Velocity (m/s) | Flow (L/min) | Flow (US gpm) |
|---|---|---|
| 0.5 | 16.7 | 4.40 |
| 1 | 33.3 | 8.81 |
| 1.5 | 50.0 | 13.21 |
| 2 | 66.7 | 17.62 |
| 2.5 | 83.4 | 22.02 |
| 3 | 100.0 | 26.42 |
Frequently asked
What is the inside diameter of 1 in schedule 40 pipe?
26.6 mm, against an outside diameter of 33.4 mm.
How much water does 1 in pipe hold?
0.556 litres per metre of run.
Where the numbers come from
- Dimensions are the ASME B36.10 schedule 40 values for the nominal size.