Pump Power Calculator
Calculate a liquid pump's hydraulic power and shaft (brake) power from flow rate, total head and fluid density, plus an optional motor input power once motor efficiency is included.
Input
The total dynamic head the pump must overcome (static lift + friction + pressure head).
When set, also computes the electrical input power the motor draws to deliver that shaft power.
Output
| Property | Value |
|---|---|
| No data yet | |
Guides
Sizing a pump means answering three different power questions: how much power the fluid itself needs (hydraulic power), how much the pump's shaft has to deliver once its own inefficiency is added (shaft/brake power), and — if you're also sizing the motor — how much electrical power the motor has to draw once its inefficiency is added on top.
The formulas
For a flow rate Q, total head H, fluid density ρ, and gravity g = 9.80665 m/s²:
Hydraulic power (kW) = ρ × g × Q × H / 1000
Shaft power (kW) = Hydraulic power ÷ pump efficiency
Motor input (kW) = Shaft power ÷ motor efficiency (optional)Q is converted to m³/s and H to meters before the calculation; results are converted back to kW and horsepower (1 kW = 1.341022 hp) for display.
Worked example: pumping 100 L/min of water through a 20 m head at 75% pump efficiency needs 0.33 kW of hydraulic power, but the pump's shaft has to deliver 0.44 kW to make up for its own losses. Add a 90%-efficient motor and the electrical draw at the wall rises to about 0.48 kW.
How to use it
- Enter the flow rate and pick its unit (L/min, m³/h, m³/min, or US GPM).
- Enter the total head — the total resistance the pump works against, including static lift, friction losses and any pressure head — and pick meters or feet.
- Pick a fluid preset (water, seawater, diesel, gasoline, glycerin) or "Custom fluid" to enter your own density.
- Enter the pump's efficiency. If you also want the motor's electrical input power, enter its efficiency too — leave it blank to stop at shaft power.
FAQ
What's the difference between hydraulic power and shaft power? Hydraulic power is the theoretical minimum power needed to move the fluid — what a perfectly efficient pump would use. Real pumps lose energy to friction, turbulence and internal leakage, so the shaft has to supply more than that; shaft power = hydraulic power ÷ pump efficiency.
Why is motor efficiency optional? Not everyone sizing a pump is also sizing its motor — sometimes you just need the mechanical shaft power a given pump curve implies. Leaving motor efficiency blank stops the calculation at shaft power; filling it in adds the electrical input power a motor with that efficiency would need to draw.
What counts as "total head"? The sum of static head (the vertical lift), friction head (losses in the piping), and any pressure head the discharge side needs — not just the physical height difference. If you only have the static lift, you'll get an optimistic (lower) power estimate.
How precise are the results? Values are shown to 4 significant figures, which is precise enough for sizing estimates. For final equipment selection, use the manufacturer's pump curve at your actual operating point.
Privacy
Everything runs locally in your browser — the numbers you enter are never uploaded or stored anywhere.
Use it from code
From 3 credits per callREST API
curl -X POST https://api.iotools.cloud/v1/tool/pump-power-calculator \
-H "Authorization: Bearer YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"flowRate": "100",
"flowUnit": "lpm",
"head": "20",
"headUnit": "m",
"fluid": "water",
"pumpEfficiency": "75"
}'Swap in your own key from your account. The tool's fields are the body — no wrapper.
Ask an AI agent
Use the IOTools `pump-power-calculator` tool (Pump Power Calculator) on this input:
YOUR_INPUT_HEREPaste this at any agent connected to the IOTools MCP server, then add your input.