Compression Temperature Rise

Estimate the discharge (“final”) temperature when a gas is compressed in one stage. Enter the suction conditions and the discharge pressure, pick the gas, and set how efficient the machine is. Works in US or SI units, for any gas — air, natural gas, refrigerants and more. Everything updates live.

Operating conditions

Suction pressure (psig)Suction temperature (°F)Discharge pressure (psig)

Atmospheric pressure (for altitude)

Atmospheric pressure (psia)

Turns gauge pressure into absolute. Sea level ≈ 14.696 psia; drop it at altitude.

Gas

Ratio of specific heats k = 1.40 (Cp/Cv). Choose Custom to set it yourself.

Compressor efficiency

Isentropic efficiency75%

How close to the ideal the machine runs. Lower efficiency means a hotter discharge. Reciprocating / screw stages are typically 0.70–0.85; centrifugal a bit higher. Set 100% for the textbook isentropic case.

Check against a measurement

I have a measured discharge temperatureBack-calculates the efficiency your machine is actually achieving.

Expected discharge

Discharge temp (actual)

634°F

At 75% isentropic efficiency

Temperature rise

564°F

Discharge minus suction

Ideal discharge

493°F

Isentropic (100% efficient) reference

Pressure ratio

7.80: 1

14.7 → 114.7 psia

Discharge temperature trend

Actual discharge temperature (°F)

Show the full calculation & assumptions

1 · Absolute pressures & temperature

Suction 0.0 psig + 14.696 = 14.7 psia
Discharge 100.0 psig + 14.696 = 114.7 psia
Suction 70 °F + 459.67 = 529.67 °R (absolute)
Pressure ratio = 114.7 ÷ 14.7 = 7.805

2 · Isentropic (ideal) discharge

T₂ = T₁ × (P₂/P₁)^(k−1)/k

k = 1.400 → exponent (k−1)/k = 0.2857
T₂ = 529.67 × 7.805^0.2857 = 952.71 °R = 493 °F
Ideal temperature rise = 423 °F

3 · Real discharge (efficiency applied)

actual rise = ideal rise ÷ η (the wasted work becomes heat)

423 °F ÷ 75% = 564 °F rise
Discharge = 70 °F + 564 °F = 634 °F

Single-stage, ideal-gas relation with a constant k. Good for a first-pass estimate; real gases near their critical point, very high ratios, or condensing streams need a full property method.

Read before you rely on these numbers

This is a single stage. Multi-stage machines with intercooling run much cooler — calculate each stage separately.
k (Cp/Cv) is taken as constant; it actually shifts with temperature and pressure. The presets are near-ambient textbook values.
Cooled compressors (oil-flooded screws, jacketed or intercooled stages) discharge below this adiabatic number — that’s why an implied efficiency can read above 100%.
Real-gas effects (compressibility, condensation) are ignored. For a guaranteed selection, confirm with manufacturer software.