Fan Power Calculator
Fan Power: Air kW = Q × Δp ÷ 1,000. Methodology stated, your own inputs only.
In short
Fan Power: Air kW = Q × Δp ÷ 1,000. Methodology stated, your own inputs only.
Formula: Air kW = Q × Δp ÷ 1,000. Shaft kW = air ÷ fan efficiency. Input kW = shaft ÷ motor efficiency.
What this calculator does
Fan Power: Air kW = Q × Δp ÷ 1,000. Methodology stated, your own inputs only. Worked example, questions and limitations included.
Use it to turn Airflow, Fan total pressure rise, Fan total efficiency (fan curve), Motor efficiency into a checked result you can compare, copy, or rerun with different assumptions.
The page shows the formula, a numeric worked example, and the assumptions that affect this energy calculation.
Inputs and what they mean
- Airflow
- — number value.
- Fan total pressure rise
- — number value.
- Fan total efficiency (fan curve)
- — number value.
- Motor efficiency
- — number value.
How to use it
- Enter each value in the unit shown next to the box (use the unit converter first if your numbers are in other units).
- Check the breakdown to see every intermediate step.
- Read the limitations before relying on the result.
Formula
Methodology: fan air power relationship from the U.S. DOE / AMCA fan system sourcebook.
Use total pressure and total efficiency together (or static with static).
Efficiencies are from the fan curve and motor data — none assumed.
Air kW = Q × Δp ÷ 1,000. Shaft kW = air ÷ fan efficiency. Input kW = shaft ÷ motor efficiency.
Inputs used: Airflow, Fan total pressure rise, Fan total efficiency (fan curve), Motor efficiency.
Worked example
An air handler
- 5 × 800 ÷ 1,000 = 4 kW.
- 4 ÷ 0.70 = 5.714 kW.
- 5.714 ÷ 0.92 = 6.2112 kW.
Reading the result
The headline figure is the main answer. Any breakdown underneath shows the parts that make it up, so you can check the working and see what changes when you adjust an input.
Limitations and assumptions
- Steady single operating point.
- Belt and drive losses not included.
- Results are estimates built only from the figures you enter. No electricity, fuel or gas price, equipment efficiency or benchmark is built in — tariffs vary by supplier, region and time, and equipment data must come from the manufacturer. Designs and installations must be checked by a qualified professional.
- The result depends on the values you enter for this fan power calculator; it does not supply missing rates, rules, prices, dates, or assumptions for you.
Reference: U.S. Department of Energy
Last reviewed:
Common questions
Total or static pressure?
Either, as long as the efficiency matches. Total pressure with total efficiency is the most common pairing.
Does air density matter?
The fan curve is for a stated density; correct the pressure to your conditions before entering it. Check the formula, example, and limitations on this page before using the result for a real energy decision.
Does this include belt losses?
No. Divide shaft power by your belt or drive efficiency if one is fitted.
How do I use the Fan Power Calculator?
Enter the required values for Airflow, Fan total pressure rise, Fan total efficiency (fan curve), Motor efficiency. The calculator applies the formula on this page and shows the main result with any supporting breakdown so you can check the arithmetic.
What formula does the Fan Power Calculator use?
Air kW = Q × Δp ÷ 1,000. Shaft kW = air ÷ fan efficiency. Input kW = shaft ÷ motor efficiency. The visible formula section above lists the calculation path and the edge cases the page handles, so the result can be checked without relying on the form alone.
Can the Fan Power Calculator be used for exact decisions?
Use it as a calculation aid, not as a substitute for checking the underlying rule, contract, policy, or professional advice that applies to your situation. When a result depends on local rules, personal details, prices, or dates, enter those values yourself and confirm them before acting.
Sources
Method based on U.S. Department of Energy.
Cite this page
Free Calculator. (2026, October 20). Fan Power Calculator. https://freecalculator.tech/tools/fan-power-calculator
"Fan Power Calculator." Free Calculator, 20 Oct. 2026, https://freecalculator.tech/tools/fan-power-calculator.
Fan Power Calculator — Free Calculator, https://freecalculator.tech/tools/fan-power-calculator
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