HVAC Ductwork, Air Handling & Mechanical Products calculator
Fan Shaft Power Calculator
Calculate fan shaft power at a specified duty point. Enter airflow, total pressure rise, matching total efficiency and the shaft rating you want to compare.
What this calculator does
- Calculate fan shaft power at a specified duty point.
Formula used
- Air power (kW) = Flow (m³/s) × Total pressure rise (Pa) ÷ 1,000
- Shaft power = Air power ÷ (Total efficiency ÷ 100)
- Headroom = Comparison shaft rating − Required shaft power
Inputs explained
- Design Airflow: Flow at the selected fan operating point.
- Fan Total Pressure Rise: Total pressure rise at the same airflow and density.
- Fan Total Efficiency: Total fan efficiency at that duty point.
- Comparison Shaft Rating: Available shaft power on the selected rating basis.
How to use the result
- Best suited to fan duty review, shaft rating comparison.
- This does not select a motor or establish the fan operating point. Drive losses and electrical input power are excluded.
Current U.S. benchmarks
- Industrial electricity averages 9.77 cents per kWh across the U.S. (EIA, Jul 2026), up 4.7% from a year earlier. Energy-intensive steps carry this directly into unit cost.
- U.S. housing starts run at 1,275k per year (Census, Aug 2026), down 1.2% from a year earlier, the demand driver for building products.
Common questions
- Can I enter static pressure? Use total pressure with total efficiency. Mixing static pressure and total efficiency gives an inconsistent duty calculation.
- Is this motor electrical demand? No. Shaft power excludes motor and drive losses.
- Does a positive margin approve the fan? No. Fan curves, density, drive limits and the actual operating point still require review.
- Why are the inputs in SI units? Flow in cubic meters per second times pressure in pascals gives watts directly.
Last reviewed 2026-10-12.