R-744 (carbon dioxide) · CO2
R-744 (carbon dioxide, CAS 124-38-9) is a single-component refrigerant; this page gives its saturation pressure and saturated liquid and vapour densities from -40 to 25 °C.
Saturation pressure and saturated liquid and vapour densities are computed from CoolProp==6.6.0 - reference Helmholtz equation of state for CO2 and tabulated over -40–25 °C.
- Also known as
- Carbon dioxide, CO2, R744, Carbonic anhydride
- CAS number
- 124-38-9
- Tabulated range
- -40–25 °C · saturation line
- Refrigerant
- R-744
- Chemical name
- carbon dioxide
- GWP (100-yr)
- 1
- ASHRAE 34 class
- A1
GWP 1 — IPCC Fourth Assessment Report (AR4, 2007), 100-year GWP. U.S. EPA - Technology Transitions GWP Reference Table. U.S. Environmental Protection Agency, Technology Transitions GWP Reference Table: R-744 (carbon dioxide, the reference gas) 100-year GWP = 1 (table reference IPCC 2007 / AR4). https://www.epa.gov/climate-hfcs-reduction/technology-transitions-gwp-reference-table
ASHRAE 34 A1 — ANSI/ASHRAE Standard 34 safety group classification. ANSI/ASHRAE Standard 34 - Designation and Safety Classification of Refrigerants. ANSI/ASHRAE Standard 34-2022, Designation and Safety Classification of Refrigerants: R-744 (carbon dioxide) assigned safety group A1.
- Saturation pressure
- 64.342bar
- Pressure
- 6434.2kPa
- Gauge
- 918.5psig
- Liquid density
- 710.5kg/m³
- Vapour density
- 242.73kg/m³
Read the saturation line either way
Set a temperature to read its saturation pressure and densities, or set a pressure to read the saturation temperature. Every number is interpolated from the committed table below and clamped to the validated -40–25 °C range — nothing is computed from a property model in your browser.
Values are interpolated along the tabulated saturation line below — both the temperature and the pressure stay within the validated -40–25 °C range and are never extrapolated.
- Saturation temp
- 25.0 °C
- Saturation pressure
- 64.342 bar
- Pressure
- 6434.2 kPa
- Gauge pressure
- 918.5 psig
- Liquid density
- 710.5 kg/m³
- Vapour density
- 242.73 kg/m³
Every tabulated point
Saturation pressure (absolute, shown in kPa and bar, with the gauge value in psig at standard atmosphere) and the saturated liquid and vapour densities at each temperature. A negative psig is a partial vacuum below one atmosphere.
| T °C | p kPa | p bar | p psig | ρ liq kg/m³ | ρ vap kg/m³ |
|---|---|---|---|---|---|
| -40 | 1004.5 | 10.045 | 131.0 | 1116.4 | 26.12 |
| -35 | 1202.4 | 12.024 | 159.7 | 1096.4 | 31.22 |
| -30 | 1427.8 | 14.278 | 192.4 | 1075.7 | 37.10 |
| -25 | 1682.7 | 16.827 | 229.4 | 1054.2 | 43.88 |
| -20 | 1969.6 | 19.696 | 271.0 | 1031.7 | 51.70 |
| -15 | 2290.8 | 22.908 | 317.6 | 1008.0 | 60.73 |
| -10 | 2648.7 | 26.487 | 369.5 | 982.9 | 71.19 |
| -5 | 3045.9 | 30.459 | 427.1 | 956.2 | 83.36 |
| 0 | 3485.1 | 34.851 | 490.8 | 927.4 | 97.65 |
| 5 | 3969.5 | 39.695 | 561.0 | 896.0 | 114.62 |
| 10 | 4502.2 | 45.022 | 638.3 | 861.1 | 135.16 |
| 15 | 5087.1 | 50.871 | 723.1 | 821.2 | 160.73 |
| 20 | 5729.1 | 57.291 | 816.2 | 773.4 | 194.20 |
| 25 | 6434.2 | 64.342 | 918.5 | 710.5 | 242.73 |
R-744 saturation pressure at a glance
At -20 °C, R-744 saturation pressure is about 19.70 bar (1970 kPa; 271.0 psig). At 0 °C, R-744 saturation pressure is about 34.85 bar (3485 kPa; 490.8 psig). At 25 °C, R-744 saturation pressure is about 64.34 bar (6434 kPa; 918.5 psig).
Where the numbers come from
Every value on this page is computed by a deterministic equation of state — none is entered by hand. The generating method and the references it is checked against:
- ▸NIST Chemistry WebBook, SRD 69 - Thermophysical Properties of Fluid Systems (REFPROP-derived saturation tables), carbon dioxide (CAS 124-38-9)
- ▸CoolProp 6.6.0 - reference Helmholtz equation of state for carbon dioxide (Span & Wagner, 1996)
- ▸U.S. EPA - Technology Transitions GWP Reference Table (100-year GWP, IPCC AR4 basis)
- ▸ANSI/ASHRAE Standard 34-2022 - Designation and Safety Classification of Refrigerants
Model: CoolProp==6.6.0 - reference Helmholtz equation of state for CO2 · Generated 2026-06-07
The committed data file for this page is published as JSON on GitHub under CC BY 4.0.
Checked against cited values
The equation of state is cross-checked against independently cited saturation points. The page is published only because every check passes.
| Property / point | Saturation pressure · 0 °C |
| Cited reference value | 3485.1 kPa |
| Model computed | 3485.14 kPa |
| Error vs reference | 0.001% (tolerance 1%) |
NIST Chemistry WebBook, SRD 69 - Thermophysical Properties of Fluid Systems. NIST Chemistry WebBook, SRD 69, Thermophysical Properties of Fluid Systems, carbon dioxide (R-744) (CAS 124-38-9), saturation curve at 0 degC: saturation pressure = 3485.1 kPa. https://webbook.nist.gov/cgi/fluid.cgi?ID=C124389&Action=Page
| Property / point | Saturated liquid density · 0 °C |
| Cited reference value | 927.43 kg/m3 |
| Model computed | 927.43 kg/m3 |
| Error vs reference | 0% (tolerance 1%) |
NIST Chemistry WebBook, SRD 69 - Thermophysical Properties of Fluid Systems. NIST Chemistry WebBook, SRD 69, Thermophysical Properties of Fluid Systems, carbon dioxide (R-744) (CAS 124-38-9), saturation curve at 0 degC: saturated liquid density = 927.43 kg/m3. https://webbook.nist.gov/cgi/fluid.cgi?ID=C124389&Action=Page
Before you use these numbers
- ▸CoolProp reference Helmholtz equation of state (Span & Wagner, 1996) for carbon dioxide. Saturation properties only, tabulated from -40 to +25 degC. The critical point is 30.98 degC / 7377.3 kPa, just above the table top: this short table ends at +25 degC by design, because vapour-compression saturation (two-phase) data above the critical point does not exist - carbon dioxide operates transcritically there, as a single supercritical phase with no distinct saturation pressure. Values are for preliminary design; verify against vendor data for critical service.
- ▸Saturation properties only — these are two-phase (saturation-line) values; superheated and sub-cooled single-phase data are out of scope for this page. The critical point is 30.98 °C / 7377.3 kPa, above the tabulated range.
- ▸Values are tabulated only inside the -40–25 °C range shown; the equation of state is not extrapolated beyond it here.
- ▸Use for preliminary design; verify for critical service.
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