How this calculator works
Multiplying fan pressure rise by actual volumetric airflow gives air power for a low-compressibility flow. Divide by overall wire-to-air efficiency to estimate electrical input. Use matching static or total pressure and efficiency definitions from the performance data. CFM is a volumetric rate, not mass flow; convert it using 1 ft3/min = 0.0004719474432 m3/s. The electrical relation VI is valid for DC; AC real power requires power factor and phase information.
Formula
Pair = Q delta p; Pin = Pair/eta; eta = Pair/Pin. DC: Pin = VI. Air density is needed only if converting mass flow to volume flow.
Worked example
A fan moving 1 m3/s through a 500 Pa rise delivers 500 W of air power. At 50% overall efficiency it draws 1000 W, equivalent to 10 A at 100 V DC.
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Frequently asked questions
Can I use standard airflow?
Use actual volume flow at the fan conditions, or correct a standard volume rate for density before calculating air power.
Is motor efficiency the overall efficiency?
No. Overall wire-to-air efficiency also includes drive and fan aerodynamic losses.
Can I calculate AC current directly?
The VI mode assumes DC or unity power factor. Use an electrical-power calculator for general single- or three-phase AC loads.