Inputs and units
Flow is in US gallons per minute and pressure is in PSI. Use the pressure difference across the pump or component being evaluated, not an unrelated system gauge reading. The efficiency percentage must apply to the same operating point and component boundary.
How the calculation works
Hydraulic hp = US GPM × pressure difference (PSI) / 1,714
Shaft hp = hydraulic hp / efficiency fraction
Modelled loss (hp) = shaft hp − hydraulic hp
Heat estimate (BTU/h) = modelled loss × 2,545The 1,714 divisor converts these flow and pressure units into mechanical horsepower. Efficiency accounts for the difference between hydraulic output and required input. The tool also expresses input in kW using 0.7457 kW per hp. Its heat estimate represents the selected efficiency loss; it is not a complete thermal model of every valve, line and actuator.
Worked example
At 10 US GPM and 2,000 PSI, hydraulic power is 20,000 ÷ 1,714 = 11.67 hp. At 80% overall efficiency the shaft requirement is 14.59 hp, or about 10.88 kW. The difference is about 2.92 hp, equivalent to roughly 7,424 BTU/h using the tool’s conversion.
Assumptions and limits
Pump efficiency varies with pressure, speed, viscosity and wear. Motor selection must also account for start conditions, service limits and the manufacturer’s performance curve. Additional throttling or relief-valve losses can dominate heat generation. Do not select a cooler solely from the efficiency-loss number or size a reservoir solely from a flow multiplier; duty cycle, ambient temperature and the complete circuit determine the thermal requirement.
References and calculation details
Page prepared September 18, 2026. Examples describe this calculator’s implementation; reference links do not imply independent certification.