Formula & example
Pair=Q·ΔP; Pinput=Pair/η.
5,000 CFM at 2 in.w.g. requires about 1.18 kW ideal air power and 1.97 kW at 60% efficiency.
HVAC engineering calculator · Updated Sep 17, 2026
Fan Power Calculator — Airflow, Static Pressure & Efficiency
Calculate ideal air power and estimated shaft/input power from airflow, pressure rise and fan efficiency.
Inputs
Result
Air power 1,175.5688 W
Estimated input/shaft power 1,959.2813 W
Estimated power 2.6274395 hp
Metric airflow 2.3597373 m³/s
Pressure rise 498.17782 Pa
Assumptions & limits
- Pressure rise is treated as the pressure useful to the air stream.
- Motor/VFD losses are excluded unless included in the entered overall efficiency.
Frequently asked questions
What does this Fan Power Calculator calculate?
Calculate ideal air power and estimated shaft/input power from airflow, pressure rise and fan efficiency.
Can I use SI and US customary units?
Yes. The calculator exposes the unit basis in the inputs and reports useful cross-unit outputs where the engineering workflow benefits from them.
Is this a replacement for HVAC design software?
No. It is a transparent deterministic engineering calculator for sizing, diagnostics and cross-checks. Final equipment, duct and refrigeration decisions should use measured conditions, manufacturer data and applicable codes or standards.