Convert GPM to kW of pump power from flow, head and pump efficiency (70% typical), or reverse kW to GPM, with results in kW, hp, L/s and m³/h.
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GPM to kW Formula
This estimates pump shaft input power from US gallons per minute, total dynamic head, fluid density and pump efficiency. Hydraulic output is Q × Δp = ρgQH. Electrical input additionally depends on motor efficiency.
Variables:
- P is pump shaft input power in kW; SG is fluid density divided by 1,000 kg/m³.
- Q is the flow rate in gallons per minute (GPM)
- H is the head in feet (ft)
- η is the efficiency (as a decimal)
Multiply US GPM, head in feet, SG and 0.000188580819, then divide by pump efficiency as a decimal. The coefficient uses standard gravity 9.80665 m/s² and the density reference 1,000 kg/m³. Pressure mode instead uses hydraulic power = flow × pressure rise, with no extra SG factor. NIST unit conversions define the US gallon, foot and mechanical horsepower conversions.
| Flow (GPM) | Shaft power (kW) |
|---|---|
| 10 | 0.269 |
| 20 | 0.539 |
| 30 | 0.808 |
| 40 | 1.078 |
| 50 | 1.347 |
| 60 | 1.616 |
| 70 | 1.886 |
| 80 | 2.155 |
| 90 | 2.425 |
| 100 | 2.694 |
| 110 | 2.963 |
| 120 | 3.233 |
| 130 | 3.502 |
| 140 | 3.772 |
| 150 | 4.041 |
| 160 | 4.310 |
| 170 | 4.580 |
| 180 | 4.849 |
| 190 | 5.119 |
| 200 | 5.388 |
| * Rounded to 3 decimals. Formula: P(kW) = Q(GPM) × H(ft) × 0.000188580819 ÷ η. Assumes H = 100 ft, η = 70%, density = 1,000 kg/m³ and standard gravity. | |
What is GPM to kW Conversion?
The GPM to kW conversion is a calculation used to estimate required power from a fluid flow, measured in gallons per minute (GPM) and head in feet, while accounting for efficiency. This conversion is important in the field of hydraulics and pump systems where efficiency is a key factor in system design and analysis.
How to Calculate Power in kW from GPM?
The following steps outline how to calculate the power in kilowatts from gallons per minute.
- First, determine the flow rate (Q) in gallons per minute.
- Next, determine the head (H) in feet.
- Next, determine the efficiency (η) as a percentage and convert it to a decimal by dividing by 100.
- Use Pshaft (kW) = Q (US GPM) × H (ft) × SG × 0.000188580819 ÷ η, with all quantities on one consistent basis.
- Finally, calculate the power (P) in kilowatts.
- After inserting the variables and calculating the result, check your answer with the calculator above.
Example Problem :
Use the following variables as an example problem to test your knowledge.
Flow rate (Q) = 50 gallons per minute
Head (H) = 100 feet
Efficiency (η) = 70%
