Compressor Power Calculator

Engineering calculator reviewed for preliminary design use · Last updated: March 2026

Calculate compressor shaft power based on adiabatic compression theory. Compute theoretical power from inlet/outlet pressure, gas flow rate, temperature, and heat capacity ratio k. Apply to compressor selection and motor sizing.

Gas Compressor Adiabatic Power

The theoretical power required to compress a gas is calculated assuming an adiabatic (isentropic) process. Actual shaft power is the adiabatic power divided by the isentropic efficiency.

Formula

P = (γ/(γ-1)) × Q × P₁ × [(P₂/P₁)^((γ-1)/γ) − 1]

  • γ: Heat capacity ratio Cp/Cv (air: 1.4, steam: 1.3, natural gas: 1.28)
  • Q: Inlet volumetric flow rate [m³/s]
  • P₁: Inlet absolute pressure [Pa]
  • P₂: Outlet absolute pressure [Pa]

Actual Shaft Power

Shaft Power = Adiabatic Power / η (isentropic efficiency, typically 0.70–0.85)

Applications

  • Air and gas compressor initial sizing
  • Refrigeration cycle compressor power estimation
  • Process gas transportation system design

Related: Gas Flow Calculator / Mach Number Calculator

Frequently Asked Questions

What efficiency should I use for preliminary sizing?

For centrifugal compressors, use 70-80% isentropic efficiency. For reciprocating compressors, 80-90%. For screw compressors, 60-75%. Actual efficiency depends on the specific machine and operating point.

Does this account for intercooling?

This calculates single-stage adiabatic power. For multi-stage compression with intercooling, calculate each stage separately and sum the power. Intercooling reduces total power and discharge temperature.

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Editorial Responsibility
  • Last reviewed: March 2026
  • Reviewed by: EngiCompute Editorial Team
  • Intended for preliminary engineering use

These results are preliminary estimates for screening-level design use. They do not replace detailed engineering, code compliance verification, or vendor-certified calculations.