Gas Compression Ratio Calculator

Plan compressor sizing with clearer ratios and temperatures. Validate multi-stage targets using practical gas properties. Export results quickly for safer field decisions everywhere daily.

Inputs
Use absolute pressures for best engineering comparability.
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Enter the measured inlet pressure.
Enter the measured outlet pressure.
Keep units consistent across all pressure inputs.
Gauge values are converted to absolute before ratio.
Used only when pressure basis is gauge.
Per-stage ratio assumes equal ratio splitting.
Used for outlet temperature and work estimation.
Temperature is internally converted to Kelvin.
Choose the exponent model for temperature/work.
Typical range: 1.2-1.4 for many gases.
Used when method is polytropic.
Adjusts ideal temperature rise and work.
Used to compute gas constant per kilogram.
Optional; enables power estimation.
Applies only when mass flow is provided.
Reset

Example Data Table

Scenario P1 P2 Basis Stages k T1 Total Ratio
Small air tool station 200 kPa 800 kPa Gauge 1 1.40 25 °C About 3.63 (abs)
Two-stage skid 1.2 bar 6.0 bar Absolute 2 1.30 20 °C 5.00
High lift temporary supply 25 psi 120 psi Gauge 3 1.28 86 °F About 4.68 (abs)

Example ratios shown for illustration; run the calculator for exact values using your atmospheric pressure.

Formula Used

Compression Ratio

The primary metric is the total compression ratio using absolute pressures: CR = P2(abs) / P1(abs). If gauge pressures are entered, atmospheric pressure is added before the ratio.

For equal ratio splitting across stages: CR(stage) = CR(total)^(1/N), where N is the number of stages.

Outlet Temperature and Work

Ideal temperature rise uses an exponent model: T2 = T1 · CR^((x−1)/x), where x = k (isentropic) or x = n (polytropic).

Specific work (kJ/kg) is estimated as: w = (x/(x−1))·R·T1·(CR^((x−1)/x) − 1)/η.

How to Use This Calculator

  1. Enter suction and discharge pressures in the same unit.
  2. Choose gauge if readings are from typical pressure gauges.
  3. Confirm atmospheric pressure for the worksite elevation.
  4. Set the number of stages to review stage ratio targets.
  5. Add inlet temperature, gas properties, and efficiency for estimates.
  6. Optionally add mass flow to estimate power demand.
  7. Download CSV or PDF after calculating for documentation.

Professional Notes

For construction sites using temporary compressors, absolute ratios help compare performance across elevations and weather. When ratios are high, consider staging or intercooling to reduce outlet temperatures and improve reliability.

If your application involves near-critical gases, high moisture, or strong real-gas effects, validate results with vendor curves and a detailed process model.

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Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.