Motor Horsepower to Pump Output Calculator
Calculate pump output flow rate (GPM) and hydraulic power from motor horsepower, pump efficiency, and system pressure.
Results will appear here.
Formulas Used
1. Hydraulic (Water) Horsepower (WHP):
WHP = Motor HP × (Efficiency / 100)
2. Pump Output Flow Rate (GPM):
GPM = (HP × 1714 × Efficiency) / (PSI × SG)
Where: 1 HP = 1714 GPM·PSI (unit conversion constant derived from 1 HP = 550 ft·lbf/s and 1 gallon = 231 in³)
3. Hydraulic Power (Watts):
Power (W) = WHP × 745.7
4. Pump Shaft Torque (informational, requires RPM):
Torque (ft·lbf) = (HP × 5252) / RPM
Assumptions & References
- The unit constant 1714 is derived from: 1 HP = 550 ft·lbf/s; 1 PSI = 144 lbf/ft²; 1 US gallon = 231 in³ → GPM = (HP × 33,000) / (PSI × 0.4335 × 8.34 × SG) ≈ HP × 1714 / (PSI × SG).
- Pump efficiency accounts for mechanical, volumetric, and hydraulic losses within the pump only; motor efficiency is not included here.
- Specific Gravity defaults to 1.0 (fresh water at ~60°F / 15.6°C). Adjust for other fluids (e.g., seawater ≈ 1.025, diesel ≈ 0.85).
- Typical centrifugal pump efficiencies range from 50% to 90%; positive displacement pumps can reach 85–95%.
- Results assume steady-state, incompressible flow with no cavitation.
- References: Hydraulic Institute Standards; Karassik et al., Pump Handbook, 4th Ed.; Crane Co. Technical Paper 410.