CO2 (R744) pressure temperature chart (PT)
CO2 (R744) saturation pressure vs temperature (PT chart): a CoolProp-generated reference table in kPa(a), bar(a), and psi(a), plus critical-point and transcritical cautions.
A CO2 (R744) pressure temperature chart (PT chart) is a saturation lookup for CO2 below the critical point: it relates temperature and saturation pressure when liquid and vapor coexist in equilibrium. This can be helpful for thermodynamic interpretation -- but CO2 systems often operate near (or above) the critical point, so PT-chart intuition must be used carefully.
Critical point warning (important for CO2)
CO2 has a relatively low critical temperature (about 30.98 deg C). Above the critical point, there is no saturation pressure/temperature relationship -- so a PT chart does not apply in the supercritical/transcritical region. Many CO2 refrigeration and heat pump cycles use a gas cooler (transcritical operation) where "condensing temperature" is not defined.
For background, see Critical point and Refrigerant PT chart.
Pressure basis: absolute vs gauge
The table below is absolute pressure (kPa(a), bar(a), psi(a)). Many gauges display gauge pressure (relative to ambient). Converting requires local atmospheric pressure:
Pabs = Pgauge + Patm
Learn more: Gauge vs absolute pressure (psig vs psia).
CO2 pressures can be high. This page is educational and is not a repair or operating guide -- always follow OEM procedures and safety requirements.
CO2 saturation pressure vs temperature (reference table)
Generated using CoolProp (the same property engine used by FluidTool) at Q=0 saturation. The table is limited to temperatures below the critical point.
| T ( deg C) | T ( deg F) | Psat (kPa(a)) | Psat (bar(a)) | Psat (psi(a)) |
|---|---|---|---|---|
| -20 | -4 | 1969.6 | 19.696 | 285.7 |
| -10 | 14 | 2648.7 | 26.487 | 384.2 |
| 0 | 32 | 3485.1 | 34.851 | 505.5 |
| 10 | 50 | 4502.2 | 45.022 | 653.0 |
| 20 | 68 | 5729.1 | 57.291 | 830.9 |
| 30 | 86 | 7213.7 | 72.137 | 1046.3 |
How to verify any row in FluidTool
- Open FluidTool with CO2 selected: /?fluid=CO2
- Choose a Two-phase input pair (Temperature & Quality / T + Q).
- Set Q=0 and enter the temperature from the table to read Psat.
For transcritical operation, PT saturation is not the right mental model for the high side -- use the full state (P+T) and look at supercritical properties instead.
Related
- CO2 (R744) data sheet: basic identifiers and thermodynamic context.
- Car A/C pressure chart: why "normal pressures" vary and what PT charts can/can't tell you.
- R1234yf PT chart: a saturation reference for a common automotive refrigerant.
- R134a PT chart: a saturation reference for R134a.
- Back to Wiki
- Open the tool
Car A/C pressure chart
What "car A/C pressure charts" are trying to show, why automotive A/C pressures vary with conditions, and how to interpret saturation vs system pressures using a PT chart.
Transcritical CO2 (R744) cycle
Learn what transcritical CO2 (R744) means, why PT charts stop working above the critical point, and how to interpret gas cooler vs condenser behavior without using "target pressures".