Water
Pipe Friction Loss Calculator
Calculate water pipe head loss and pressure loss using the Hazen–Williams equation.
Use the actual internal diameter, not nominal pipe size.
Higher values represent smoother pipe surfaces.
Head Loss
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Estimated friction head loss across the entered straight pipe length.
Head loss
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Head loss
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Pressure loss
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Pressure loss
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Pressure loss
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Friction loss per 100 m
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Flow velocity
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Hazen–Williams C
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Method:
The calculator uses the SI form of the Hazen–Williams equation:
hf = 10.67 × L × Q1.852 ÷ (C1.852 × d4.87)
where hf is head loss in metres, L is pipe length in metres, Q is flow in m³/s, C is the Hazen–Williams coefficient and d is internal pipe diameter in metres.
Pressure loss is calculated from water head using approximately 9.80665 kPa per metre of water.
Hazen–Williams is an empirical method intended primarily for water flow in pressurized pipes. It does not include losses through valves, bends, tees, entrances or other fittings. Those minor losses should be added separately where important.