Calculate compressor discharge pressure from suction pressure and an absolute pressure ratio, with consistent gauge/absolute references and pressure units.

Pressure ratio means P₂ absolute / P₁ absolute, not piston volume ratio. Use the same pressure basis at suction and discharge; this tool does not calculate temperature, power or equipment limits.

Enter 3 for a 3:1 pressure ratio.

Default is an approximate standard atmosphere in PSI. Enter the actual gauge reference pressure.

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Compressor Discharge Pressure Formula

The following formula calculates discharge absolute pressure from suction absolute pressure and their pressure ratio. It does not use the piston volume compression ratio.

Pd = Pₛ × CR

Variables:

  • P_d is the compressor discharge absolute pressure
  • P_s is the compressor suction absolute pressure
  • CR is the absolute discharge/suction pressure ratio, P_d / P_s (at least 1 for compression)

Multiply absolute suction pressure by the absolute pressure ratio. For gauge suction, first add the atmospheric reference; subtract the same reference from absolute discharge pressure for gauge discharge pressure.

What is Compressor Discharge Pressure?

Compressor discharge pressure is the pressure of the gas or air after it has been compressed by the compressor. This pressure is typically higher than the suction pressure, which is the pressure of the gas or air before it enters the compressor. The discharge pressure is a critical parameter in many industrial and mechanical applications, as it determines the efficiency and performance of the compressor system. It is influenced by factors such as the type of compressor, the compression ratio, and the properties of the gas being compressed.

How to Calculate Compressor Discharge Pressure?

The following steps outline how to calculate the Compressor Discharge Pressure.

  1. First, determine suction pressure and select its gauge or absolute reference. Set the atmospheric reference used for gauge conversion.
  2. Next, determine the absolute pressure ratio P_d / P_s (CR). A piston volume ratio is not interchangeable with this ratio.
  3. Finally, calculate the compressor discharge pressure using the formula P_d = P_s * CR.
  4. After inserting the values and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

Compressor suction pressure (P_s) = 100 kPa absolute

Absolute pressure ratio (CR) = 5, giving discharge pressure 500 kPa absolute. With a 101.325 kPa atmospheric reference, discharge gauge pressure is 398.675 kPa.