Work out air compressor sizing instantly with clear inputs, formula shown and shareable results.
Adiabatic compression power is (P1 Q / 229) x k/(k-1) x [(P2/P1)^((k-1)/k) - 1] with k = 1.4 for air. Dividing by compressor efficiency gives shaft power. The result explains the familiar rule of about four SCFM per horsepower at 100 psig, and why raising pressure costs power out of proportion to the air gained.
Adiabatic power
hp = (P1 x Q / 229) x 3.5 x [(P2/P1)^0.2857 - 1]
Shaft power
BHP = theoretical hp / efficiency
hp = (P1 x Q / 229) x 3.5 x [(P2/P1)^0.2857 - 1]. Adiabatic compression power is (P1 Q / 229) x k/(k-1) x [(P2/P1)^((k-1)/k) - 1] with k = 1.4 for air.
Power rises with the pressure ratio term, so every 2 psi of unnecessary discharge pressure costs roughly 1 percent more energy for the same air delivered.
This calculator takes 3 inputs: Air demand, Discharge pressure, Compressor efficiency. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.