Hazen-Williams Pipe Flow Calculator
Compute flow velocity or friction head loss in pressurized pipes using the Hazen-Williams equation.
Hazen-Williams equation
SI: V = 0.849 · C · R0.63 · S0.54 (V in m/s, R in m)
US: V = 1.318 · C · R0.63 · S0.54 (V in ft/s, R in ft)
Head loss (SI): hf = 10.67 · L · Q1.852 / (C1.852 · d4.87)
Valid for water at ~20 °C in turbulent flow; R = hydraulic radius (d/4 for a full circular pipe).
SI: V = 0.849 · C · R0.63 · S0.54 (V in m/s, R in m)
US: V = 1.318 · C · R0.63 · S0.54 (V in ft/s, R in ft)
Head loss (SI): hf = 10.67 · L · Q1.852 / (C1.852 · d4.87)
Valid for water at ~20 °C in turbulent flow; R = hydraulic radius (d/4 for a full circular pipe).
Typical C values
| Pipe material | C |
|---|---|
| PVC / HDPE (new) | 150 |
| Ductile iron, cement-lined | 130–140 |
| Steel (new) | 130–140 |
| Concrete | 120 |
| Cast iron (old) | 100 |