Pump Power Calculator — Formule
## Pump Power Calculation
The power a pump must supply depends on the flow rate, the head it must overcome, and pump efficiency.
### Formulas
**Hydraulic power = rho g Q H** (useful work on the fluid)
**Shaft power = rho g Q H / eta** (actual input from motor)
where rho is fluid density, g = 9.81 m/s^2, Q is volumetric flow rate, H is total dynamic head, and eta is pump efficiency.
The power a pump must supply depends on the flow rate, the head it must overcome, and pump efficiency.
### Formulas
**Hydraulic power = rho g Q H** (useful work on the fluid)
**Shaft power = rho g Q H / eta** (actual input from motor)
where rho is fluid density, g = 9.81 m/s^2, Q is volumetric flow rate, H is total dynamic head, and eta is pump efficiency.
Exemple Résolu
A pump delivers 20 L/s of water against 30 m total head at 75% efficiency.
- Q = 20 L/s = 0.020 m^3/s
- Hydraulic power = 1000 x 9.81 x 0.020 x 30 = 5886 W = 5.89 kW
- Shaft power = 5.89 / 0.75 = 7.85 kW
- Select a motor of at least 7.5 kW (next standard size up).