Pump · calculator
Hydraulic Horsepower Calculator (PSI & GPM to Water HP)
Convert PSI and GPM into hydraulic horsepower, then estimate required input horsepower from pump efficiency.
Method record
What this calculator measures
The constant 1714 combines US customary pressure, volume, time, and horsepower units. The equation gives ideal power transferred to the liquid, not the motor nameplate size.
Hydraulic HP = PSI × GPM ÷ 1714 Use it correctly
Calculation steps
- Use pressure rise across the pump, not an unrelated gauge reading.
- Use the pump's actual operating flow.
- Apply expected efficiency to estimate input horsepower.
Applicability
Use the model within its limits
Motor selection also needs service factor, duty cycle, drive losses, and the manufacturer pump curve.
What this result represents
- System
- Pump
- Formula
- Hydraulic HP = PSI × GPM ÷ 1714
- Review
- Verify safety-sensitive work with qualified guidance.
Worked Field Example
Worked Example: Industrial Booster Pump Power Requirement
Field Scenario: Sizing an electric motor for a water booster pump operating at 120 GPM and 85 PSI with 72% pump hydraulic efficiency and 90% motor efficiency.
Given Input Parameters
Step-by-Step Mathematical Solution
- Calculate Hydraulic Horsepower (water power): Whp = (85 × 120) / 1714 = 10,200 / 1714 ≈ 5.95 HP.
- Calculate Brake Horsepower (pump shaft power required): BHP = 5.95 / 0.72 ≈ 8.26 HP.
- Calculate Electrical Power Consumed: Electric HP = 8.26 / 0.90 ≈ 9.18 HP (6.85 kW).
5.95 Whp net fluid power; requires a standard 10.0 HP electric motor.
Professional Guidance: Always select the next larger standard NEMA motor rating (10 HP) to prevent motor overload during high-flow startup.
Engineering FAQs
Frequently Asked Questions
Why is 1714 the divisor in the hydraulic horsepower equation?
1714 is derived from mechanical energy conversion constants: 1 HP = 33,000 ft-lb/min. Since 1 PSI = 144 lb/ft² and 1 gallon = 0.13368 ft³, power = (P × 144) × (Q × 0.13368) / 33,000 = (P × Q) / 1714.08.
What is the difference between Hydraulic HP, Brake HP, and Motor HP?
Hydraulic HP (or water HP) is the net mechanical power transferred directly to the water. Brake HP (BHP) is the mechanical power required at the pump shaft, accounting for impeller friction and mechanical losses. Motor HP represents the total electrical power consumed from the power line.
What happens to pump horsepower when operating pressure or flow changes?
Power is directly proportional to both pressure and flow. Doubling the flow rate at constant pressure doubles the required horsepower. Under centrifugal pump affinity laws, changing impeller speed alters horsepower by the cube of the speed ratio.