Saturation Properties Calculator
Bubble and dew saturation pressures at any temperature, plus the refrigerant's reference properties (critical point, normal boiling point, molar mass). Foundation data for service measurements, retrofit comparisons, and engineering design.
Updated October 26, 2026
- Bubble pressure
- 118.79 PSIG 819.0 kPa
- Dew pressure
- 118.35 PSIG 816.0 kPa
Refrigerant properties at standard conditions
- Boiling point @ 1 atm
- −51.4°C / −60.6°F
- Critical point
- —
- Molar mass
- 72.58 g/mol
- Temperature glide at 0°C
- 0.19°F (negligible)
Saturation properties — the thermodynamic backbone of HVAC service
Every refrigerant's service behavior is anchored by its saturation curve: the locus of points in the pressure-temperature plane where liquid and vapor coexist in equilibrium. The curve starts at the triple point (where solid, liquid, and vapor meet) and ends at the critical point (where the phases merge into a supercritical fluid).
On the curve, pressure and temperature are coupled: knowing one tells you the other. Above the curve (higher P or lower T) the refrigerant is liquid; below the curve (lower P or higher T) it's vapor; on the curve it's a two-phase mixture. The saturation curve is what makes service manifold gauges useful — read a pressure, look up the saturation temperature, infer the phase state.
Pressure-temperature phase diagram for a pure refrigerant. The saturation curve (solid line) bounds the two-phase region. Above the critical point no phase distinction exists. Below the triple point the refrigerant cannot be liquid at any pressure. Source: ASHRAE Handbook—Refrigeration (2022), vapor-compression cycle thermodynamics.
Reference properties across mainstream refrigerants
| Refrigerant | T_crit (°F) | P_crit (PSIA) | NBP (°F) | Molar mass (g/mol) |
|---|---|---|---|---|
| R-22 | 205.1 | 723.7 | −41.5 | 86.5 |
| R-32 | 172.6 | 838.6 | −61.0 | 52.0 |
| R-410A | — | — | −60.6 | 72.6 |
| R-454B | — | — | −58.9 | 62.6 |
| R-134a | 213.8 | 588.7 | −14.9 | 102.0 |
| R-407C | — | — | −46.5 | 86.2 |
| R-404A | — | — | −51.2 | 97.6 |
| R-454C | — | — | −50.0 | 90.8 |
| R-1234yf | 202.5 | 490.5 | −21.1 | 114.0 |
| R-744 (CO₂) | 87.8 | 1070.0 | none: no liquid phase at 1 atm (triple point −69.8°F) | 44.0 |
| R-290 (propane) | 206.1 | 616.6 | −43.8 | 44.1 |
| R-717 (NH₃) | 270.3 | 1648.1 | −28.0 | 17.0 |
Critical temperature visualization across pure HVAC refrigerants. R-744 (CO₂) has the lowest critical temperature (87.8°F) — below typical hot-weather ambient — which is why R-744 commercial refrigeration often operates transcritically. Ammonia (R-717) has the highest critical temperature (270°F) and is the most thermodynamically capable refrigerant for industrial applications. Source: the site's PT dataset (CoolProp 7.2.0).
Normal boiling point — the application envelope anchor
The normal boiling point (NBP) — saturation temperature at 1 atm absolute — is the most useful single-number characterization of a refrigerant's service envelope. Refrigerants with low NBP work in cold applications without the system going into vacuum on the suction side; refrigerants with high NBP avoid excessive high-side pressure but can't maintain low evaporator temperatures.
Real engineering scenarios using saturation properties
Two field questions: where the R-410A high-pressure switch opens, and when a CO₂ system switches to transcritical operation at its critical temperature.
Where the R-410A high-pressure switch opens
Scenario · R-410A residential AC. Where does the OEM high-pressure safety switch open and reset?
CO₂ supermarket — when does the system go transcritical?
Scenario · R-744 transcritical supermarket commercial refrigeration system in northern climate. Operator asks: at what outdoor ambient does the system switch from sub-critical to transcritical operation?
When to use this calculator vs the others
- Saturation Properties (this page) — broad saturation reference with bubble, dew, critical point, NBP, molar mass. Best for engineering design, cycle calculations, learning thermodynamic context.
- PT Calculator — focused bidirectional lookup for service measurement. Faster for in-the-field use.
- Superheat Calculator — applies saturation values to suction-line measurements.
- Subcooling Calculator — applies saturation values to liquid-line measurements.
- PT Comparison Tool — visual overlay of multiple refrigerants' saturation curves.
- Per-refrigerant detail pages — full reference for any refrigerant in the dataset, with PT charts, properties, lubricant, safety, and replacement options.
Primary sources
- CoolProp 7.2.0 (Bell, Wronski, Quoilin, Lemort 2014, doi:10.1021/ie4033999) — REFPROP-compatible Helmholtz EOS for all saturation and reference properties.
- NIST REFPROP 10.0 (Lemmon, Bell, Huber, McLinden 2018, doi:10.18434/T4/1502528) — Reference Fluid Thermodynamic and Transport Properties Database. CoolProp cross-checks against REFPROP for accuracy.
- ASHRAE Standard 34-2022 — Designation and Safety Classification of Refrigerants. Normal boiling points and reference designation.
- ASHRAE Handbook—Refrigeration (2022) — vapor-compression cycle, lubricants, and “Equipment and System Dehydrating, Charging, and Testing” (service procedures). Phase diagram explanations, saturation property usage in cycle calculations.
- NIST WebBook — chemical properties, molar masses, CAS registry references.
- Manufacturer technical datasheets— Chemours and Honeywell saturation tables for the two R-404A retrofit blends CoolProp does not model (R-438A, R-448A), and Chemours’ Opteon XP30 charts for R-514A. Newer low-GWP fluids (R-450A, R-515A/B, R-1224yd(Z), R-1336mzz(Z)) are computed with CoolProp 8.0.0.
- [1]Residential Air Conditioners and Heat Pumps Using R-22 and Puron Refrigerant: Application Guideline and Service Manual, Catalog No. 24-25-2SM. Carrier. 04/08. https://www.shareddocs.com/hvac/docs/1009/Public/07/24-25-2SM.pdf (accessed October 20, 2026). p. 13, High-Pressure Switch — high-pressure-switch cutout settings and high-head causes.
How to read your results
- Bubble pressure (PSIG / kPa)
- Saturation pressure of the liquid at your temperature — the point where the first vapor bubble forms. This is the value to apply to liquid-line readings for subcooling; for pure refrigerants and azeotropes it equals the dew pressure.
- Dew pressure (PSIG / kPa)
- Saturation pressure of the vapor at your temperature — the point where the last liquid drop evaporates. Use this value against suction-line readings for superheat, especially on zeotropic blends where it differs from bubble pressure.
- Boiling point @ 1 atm (normal boiling point)
- Saturation temperature at atmospheric pressure (0 PSIG). A low NBP well below 0°F means the refrigerant stays above atmospheric across AC and refrigeration ranges; a higher NBP points toward chiller or high-temperature service.
- Critical point (temperature, pressure)
- The temperature and pressure above which liquid and vapor become indistinguishable and no saturation state exists — the thermodynamic ceiling for the high side. Operating near or above the critical temperature means transcritical behavior (mainly relevant for R-744/CO₂).
- Molar mass (g/mol)
- The refrigerant's molecular weight, a fixed reference property that does not change with temperature. It feeds cycle and mass-flow calculations and helps identify blends versus pure fluids.
- Temperature glide at 0°C (significant / negligible)
- The stored temperature glide in °F, flagged significant or negligible. Significant glide (blends such as R-407C or R-455A) means you must use dew for superheat and bubble for subcooling; negligible glide means a single saturation temperature applies throughout the phase change.
How to use this calculator
- Pick the refrigerant from the dropdown. Defaults to R-410A.
- Enter the temperature of interest in °F or °C.
- Read the bubble and dew pressures (PSIG and kPa shown side-by-side). For pure refrigerants and azeotropes bubble = dew.
- Reference properties (critical T, critical P, NBP, molar mass) shown alongside the saturation values.
- Use the result to interpret service measurements, do cycle calculations, or compare against alternative refrigerants.
Common errors
- Confusing PSIG and PSIA — manifold gauges read PSIG; PSIA = PSIG + 14.696.
- Using bubble pressure for superheat calculations on zeotropic blends — use dew curve at suction pressure.
- Trying to look up properties above the critical temperature — no saturation state exists there, so the calculator reports that the temperature is outside the refrigerant's chart range.
- Treating the chart range (−40 to 150°F) as universal — some refrigerants have narrower validity (R-744 critical at 87.8°F).
Underlying math
Formula
Saturation properties from CoolProp 7.2.0: P_sat,bubble(T) = saturated liquid pressure at temperature T P_sat,dew(T) = saturated vapor pressure at temperature T Glide(T) = T_sat,dew(P) − T_sat,bubble(P) at the same pressure Reference properties: T_critical = temperature above which no phase distinction P_critical = pressure at critical point T_NBP = saturation T at 1 atm absolute (0 PSIG) M = molar mass
Source
All saturation properties from CoolProp 7.2.0 (Bell, Wronski, Quoilin, Lemort 2014, doi:10.1021/ie4033999), REFPROP-compatible Helmholtz EOS. Critical points cross-checked against NIST REFPROP 10.0 (NIST Standard Reference Database 23). Normal boiling points per ASHRAE Standard 34-2022. Molar masses per CAS Registry / NIST WebBook.
Worked example
R-410A at 70°F: Bubble pressure: 201.8 PSIG (PSIA = 216.5) Dew pressure: 201.1 PSIG (PSIA = 215.8) Glide at 0°C: 0.19°F Critical T: — Critical P: — NBP: −60.6°F Molar mass: 72.58 g/mol R-407C at 70°F: Bubble pressure: 140.5 PSIG (PSIA = 155.2) Dew pressure: 117.3 PSIG (PSIA = 132.0) Glide at 0°C: 11.02°F Critical T: — Critical P: — NBP: −46.5°F Molar mass: 86.20 g/mol
Related tools
PT Calculator
Bidirectional temperature ↔ pressure lookup for service use.
Superheat Calculator
Apply dew pressure to suction-line measurements.
Subcooling Calculator
Apply bubble pressure to liquid-line measurements.
PT Comparison Tool
Visual overlay of 2-4 refrigerant saturation curves.
R-410A detail page
Full reference for R-410A and 50+ other refrigerants.
Frequently asked
›What is saturation pressure?
Saturation pressure is the pressure at which a refrigerant exists as both liquid and vapor in equilibrium at a given temperature. For pure refrigerants and azeotropes, a single saturation pressure corresponds to each temperature. For zeotropic blends there are two values: bubble pressure (saturated liquid — where vapor first forms) and dew pressure (saturated vapor — where the last liquid disappears). Service technicians use saturation pressure to interpret manifold gauge readings via the PT chart relationship.
›Why do bubble and dew differ for blends?
Zeotropic refrigerant blends are mixtures of components with different normal boiling points. At constant pressure, the more volatile component vaporizes preferentially, shifting the composition of the remaining liquid as evaporation progresses. The saturation temperature changes during the phase transition — the difference between starting (bubble) and ending (dew) is the temperature glide. R-407C has ~11°F glide; R-454C ~14°F; R-455A ~22°F; R-410A is near-azeotropic with ~0.2°F glide.
›What is the critical point and why does it matter?
The critical point is the temperature and pressure above which the liquid and vapor phases become indistinguishable — there is no boiling, no condensation, no separate phases. Above the critical temperature, the refrigerant is a supercritical fluid. R-744 (CO₂) has a critical temperature of 87.8°F, which is why CO₂ refrigeration systems often operate transcritically in warm climates (high-side above the critical point). HFCs like R-410A have much higher critical temperatures (160°F) so they always operate sub-critically in HVAC service.
›What is the triple point?
The triple point is the unique temperature and pressure at which solid, liquid, and vapor coexist in equilibrium. Below the triple-point temperature the refrigerant cannot exist as liquid at any pressure — only solid or vapor. Most HVAC refrigerants have triple-point temperatures well below normal service ranges (R-410A: −238°F; R-134a: −156°F), so triple-point behavior is irrelevant for routine HVAC. CO₂ is an exception: triple point at −69.8°F, which matters for low-temp R-744 system design and refrigerant handling.
›What's the difference between absolute and gauge pressure?
Absolute pressure is measured from a perfect vacuum (0 PSIA = vacuum). Gauge pressure is measured from atmospheric (0 PSIG = atmospheric, approximately 14.696 PSIA at sea level). Service manifold gauges read PSIG by default. This calculator reports PSIG; for PSIA, add 14.696. Likewise the kPa values are gauge — for kPa absolute, add 101.325.
›Why is normal boiling point a key refrigerant property?
Normal boiling point (NBP) is the temperature at which the refrigerant boils at 1 atm (14.696 PSIA, 0 PSIG). It anchors the saturation curve and tells you the range of HVAC applications the refrigerant fits. Low NBP refrigerants (R-32 NBP = −62°F, R-410A NBP = −60°F) work for AC and commercial refrigeration; R-744 has no liquid phase at 1 atm (triple point −69.8°F). Higher NBP refrigerants (R-134a NBP = −15°F, R-1233zd NBP = +65°F) are used for chillers and high-temperature applications.
›How does this calculator differ from the PT calculator?
The PT calculator is a focused bidirectional lookup (enter T → get P, or enter P → get T). This calculator emphasizes the broader saturation properties: bubble, dew, critical point, normal boiling point, and reference physical properties (molar mass). Use the PT calculator for in-the-field service measurements; use this one for engineering design, cycle calculations, or learning the thermodynamic context.