Calculate pump power, flow, head, or efficiency from GPM, head, and efficiency, with results in kW, HP, W, feet, meters, L/s, and m³/h.
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GPM to kW Formula
The following formula is used to calculate the power in kilowatts (kW) from gallons per minute (GPM), head in feet, and efficiency.
P (kW) = (Q (GPM) * H (ft) * .0001887) / η
Variables:
- P is the power in kilowatts (kW)
- Q is the flow rate in gallons per minute (GPM)
- H is the head in feet (ft)
- η is the efficiency (as a decimal)
To calculate the power in kilowatts, multiply the flow rate in gallons per minute by the head in feet and the constant 0.0001887, then divide by the efficiency (as a decimal). (This constant assumes water with specific gravity ≈ 1.)
| Flow (GPM) | Power (kW) |
|---|---|
| 10 | 0.270 |
| 20 | 0.539 |
| 30 | 0.809 |
| 40 | 1.078 |
| 50 | 1.348 |
| 60 | 1.617 |
| 70 | 1.887 |
| 80 | 2.157 |
| 90 | 2.426 |
| 100 | 2.696 |
| 110 | 2.965 |
| 120 | 3.235 |
| 130 | 3.504 |
| 140 | 3.774 |
| 150 | 4.044 |
| 160 | 4.313 |
| 170 | 4.583 |
| 180 | 4.852 |
| 190 | 5.122 |
| 200 | 5.391 |
| * Rounded to 3 decimals. Formula: P(kW) = Q(GPM) × H(ft) × 0.0001887 ÷ η. Assumes H = 100 ft and η = 70%. | |
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.
- Next, gather the formula from above = P (kW) = (Q (GPM) * H (ft) * 0.0001887) / η.
- 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%