16 in schedule 40 pipe flow and volume calculator
16 in schedule 40 pipe has an outside diameter of 406.4 mm and a bore of 381 mm, a wall thickness of 12.70 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
- 2710.624
- Inside diameter
- 381.00
- Wall thickness
- 12.700
- Bore area
- 114 009.18 mm2
- Water content per metre
- 114.0092
- Water in the run
- 2850.23
- Weight of that water
- 2850.23
- Friction head loss
- 0.118
- Pressure drop
- 1.157 kPa
Show the working
- Flow velocity = 1.5
- Pipe run = 25
- Hazen-Williams C = 140
- Fluid density = 1000
- Inside diameter = 381 = 381
- outside = 406.4 = 406.4
- Wall thickness = (406.4 - 381) / 2 = 12.7
- Bore area = pi * 381^2 / 4 = 114 009
- area_m2 = 114 009 / 1e6 = 0.114 009
- Water content per metre = 114 009 / 1000 = 114.009
- Water in the run = 114.009 * 25 = 2850.23
- flow_m3s = 0.114 009 * 1.5 = 0.171 014
- Flow at that velocity = 0.171 014 * 60000 = 10 260.8
- Flow in US gallons per minute = 10 260.8 / 3.785411784 = 2710.62
- loss_per_m = 10.67 * (0.171 014)^1.852 / (140^1.852 * (381/1000)^4.87) = 0.004 720 68
- Friction head loss = 0.004 720 68 * 25 = 0.118 017
- Pressure drop = 0.118 017 * 1000 * g0 / 1000 = 1.157 35
- Weight of that water = 2850.23 * 1000 / 1000 = 2850.23
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.
16 in pipe at common velocities
| Velocity (m/s) | Flow (L/min) | Flow (US gpm) |
|---|---|---|
| 0.5 | 3420.3 | 903.54 |
| 1 | 6840.6 | 1807.08 |
| 1.5 | 10260.8 | 2710.62 |
| 2 | 13681.1 | 3614.16 |
| 2.5 | 17101.4 | 4517.71 |
| 3 | 20521.7 | 5421.25 |
Frequently asked
What is the inside diameter of 16 in schedule 40 pipe?
381 mm, against an outside diameter of 406.4 mm.
How much water does 16 in pipe hold?
114.009 litres per metre of run.
Where the numbers come from
- Dimensions are the ASME B36.10 schedule 40 values for the nominal size.