4 in schedule 40 pipe flow and volume calculator
4 in schedule 40 pipe has an outside diameter of 114.3 mm and a bore of 102.3 mm, a wall thickness of 6.00 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
- 195.421
- Inside diameter
- 102.30
- Wall thickness
- 6.000
- Bore area
- 8219.42 mm2
- Water content per metre
- 8.2194
- Water in the run
- 205.49
- Weight of that water
- 205.49
- Friction head loss
- 0.547
- Pressure drop
- 5.362 kPa
Show the working
- Flow velocity = 1.5
- Pipe run = 25
- Hazen-Williams C = 140
- Fluid density = 1000
- Inside diameter = 102.3 = 102.3
- outside = 114.3 = 114.3
- Wall thickness = (114.3 - 102.3) / 2 = 6
- Bore area = pi * 102.3^2 / 4 = 8219.42
- area_m2 = 8219.42 / 1e6 = 0.008 219 42
- Water content per metre = 8219.42 / 1000 = 8.219 42
- Water in the run = 8.219 42 * 25 = 205.485
- flow_m3s = 0.008 219 42 * 1.5 = 0.012 329 1
- Flow at that velocity = 0.012 329 1 * 60000 = 739.748
- Flow in US gallons per minute = 739.748 / 3.785411784 = 195.421
- loss_per_m = 10.67 * (0.012 329 1)^1.852 / (140^1.852 * (102.3/1000)^4.87) = 0.021 869 9
- Friction head loss = 0.021 869 9 * 25 = 0.546 749
- Pressure drop = 0.546 749 * 1000 * g0 / 1000 = 5.361 77
- Weight of that water = 205.485 * 1000 / 1000 = 205.485
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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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.
4 in pipe at common velocities
| Velocity (m/s) | Flow (L/min) | Flow (US gpm) |
|---|---|---|
| 0.5 | 246.6 | 65.14 |
| 1 | 493.2 | 130.28 |
| 1.5 | 739.7 | 195.42 |
| 2 | 986.3 | 260.56 |
| 2.5 | 1232.9 | 325.70 |
| 3 | 1479.5 | 390.84 |
Frequently asked
What is the inside diameter of 4 in schedule 40 pipe?
102.3 mm, against an outside diameter of 114.3 mm.
How much water does 4 in pipe hold?
8.219 litres per metre of run.
Where the numbers come from
- Dimensions are the ASME B36.10 schedule 40 values for the nominal size.