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.

Refrigerant

Temp unit

Saturation temperature (°F)

Bubble pressure: 118.79PSIG819.0kPa
Dew pressure: 118.35PSIG816.0kPa
Glide: 0.44PSIG3.0kPa

Refrigerant properties at standard conditions

Boiling point @ 1 atm: -51.4°C / -60.6°F
Critical point: No single point (blend critical locus)
Molar mass: 72.58 g/mol
Temperature glide at 0°C: -0.19°F (negligible)

About density and enthalpy

Liquid density, vapor density, and enthalpy of vaporization are available from CoolProp for pure refrigerants but require an extension to the data generator. Pending that work, this calculator returns saturation pressures and the reference properties stored in the dataset. For enthalpy and density today, query CoolProp directly with the refrigerant identifier shown on the refrigerant's detail page.

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 of Refrigeration 2022 Chapter 1 (vapor-compression cycle thermodynamics).

One curve, everything follows

Superheat, subcooling, expansion-device sizing, charge calculations, retrofit decisions — every HVAC service calculation traces back to the saturation curve. This calculator gives you the foundation data; the other site calculators apply it to specific service scenarios.

Reference properties across mainstream refrigerants

Critical point, normal boiling point, molar mass

Refrigerant	T_crit (°F)	P_crit (PSIA)	NBP (°F)	Molar mass (g/mol)	Notes
R-22	205.1	722.2	−41.4	86.5	Legacy HCFC, phased out 2020
R-32	172.6	838.8	−61.8	52.0	A2L, dominant in Asia
R-410A	160.4	712.8	−60.0	72.6	A1 HFC blend, near-azeotropic
R-454B	170.5	756.0	−58.4	62.6	A2L, leading R-410A replacement in NA
R-134a	213.9	589.0	−15.2	102.0	Chiller / mobile AC HFC
R-407C	187.0	689.4	−47.4	86.2	R-22 retrofit zeotrope
R-404A	161.6	540.4	−51.6	97.6	Legacy LT commercial HFC, AIM Act
R-454C	181.0	643.0	−51.3	90.8	A2L LT commercial replacement
R-1234yf	200.7	488.2	−20.9	114.0	Mobile AC HFO
R-744 (CO₂)	87.8	1071.4	−108.4	44.0	Transcritical above 87.8°F
R-290 (propane)	206.1	617.4	−43.7	44.1	A3 hydrocarbon, low GWP
R-717 (NH₃)	270.3	1645.8	−28.0	17.0	B2L industrial refrigeration

Critical temperature visualization across 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: CoolProp 7.2.0 cross-checked against NIST REFPROP 10.0.

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.

NBP by application family

Application	Typical evap T	Typical refrigerants (NBP)
Cryogenics	below −150°F	R-23 (NBP −115°F), R-14 (NBP −198°F)
Ultra-low-temp medical / freezer	−100°F to −60°F	R-744 (NBP −108°F), R-744 / R-290 cascades
Low-temp commercial	−40°F to −10°F	R-404A (NBP −52°F), R-454C, R-455A
Medium-temp commercial	10°F to 30°F	R-448A, R-449A, R-407A
Residential / light commercial AC	40°F to 50°F	R-410A (NBP −60°F), R-32, R-454B, R-22
Mobile AC	35°F to 45°F	R-1234yf (NBP −21°F), R-134a
Centrifugal chiller	40°F to 50°F	R-134a (NBP −15°F), R-513A, R-1234ze (NBP +0°F)
High-temp / industrial process	100°F to 250°F	R-1233zd (NBP +65°F), R-1336mzz

Real engineering scenarios using saturation properties

Five scenarios showing how saturation properties anchor engineering decisions: retrofit envelope check, cycle calculation for capacity sizing, critical-point relevance for CO₂ system design, evaporator design for chiller, low-temp refrigerant selection.

Service problemR-410A

Compressor discharge above critical point — protection cutout sizing

Scenario · R-410A residential AC. The high-pressure safety cutout needs to be set below the critical pressure to prevent operation in the supercritical regime. What's the value to set?

Saturation properties referenced

R-410A T_critical160.4°Ffrom this calculator

R-410A P_critical712.8 PSIA = 698 PSIGabsolute - 14.7

Cutout sizing logic

Standard HPS cutout = 0.85 × P_criticalcommon safety factor

Cutout = 0.85 × 698 = 593 PSIGCarrier / Trane R-410A residential default 600-650 PSIG

Result · High-pressure cutout typically set at 600-650 PSIG

Below the critical pressure (698 PSIG) with margin. Industry-standard cutout settings on R-410A residential equipment fall in 600-650 PSIG range — well below critical to protect against runaway and the system operating in unstable near-critical regime where small temperature changes cause large pressure excursions.

Service problemR-744 (CO₂)

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?

Saturation properties

R-744 T_critical87.8°Ffundamental property

R-744 P_critical1071.4 PSIA = 1057 PSIGhigh-pressure system

R-744 T_triple−69.8°Fbelow this T, no liquid CO₂

Result · Transcritical above 87.8°F outdoor

When outdoor air temperature exceeds 87.8°F (R-744 critical T), the gas cooler (high side) operates supercritically — there is no condensation, just sensible gas cooling. Below 87.8°F outdoor the system operates sub-critically with normal condensation. Most R-744 supermarket systems are designed to handle both modes and switch automatically via the high-pressure throttle valve setpoint.

Fix

R-744 system design must account for both regimes: sub-critical condenser / transcritical gas cooler. Components are rated for transcritical pressures (typically 130 bar / 1900 PSIG design pressure). The high-pressure valve modulates to optimize system COP based on whether the cycle is sub-critical or transcritical at the current ambient.

Service problemR-1234ze (chiller)

Chiller refrigerant selection — why R-1234ze NBP matters

Scenario · New centrifugal chiller specification. R-1234ze is being considered as a low-GWP HFO option for new chiller plants. What's special about R-1234ze's NBP that affects chiller design?

Saturation properties comparison

R-134a NBP−15.2°Fstandard chiller HFC

R-1234ze NBP+0.0°F (15.4°F warmer)low-pressure HFO

R-1234ze P @ 45°F evap~5 PSIG (vs R-134a 40 PSIG)much lower

Result · R-1234ze runs in mild vacuum on the evaporator side

R-1234ze's NBP at 0°F means at typical chiller evaporator temperatures (45°F), the saturation pressure is only ~5 PSIG — barely above atmospheric and close to entering vacuum for slightly colder evap temps. R-1234ze chiller systems are designed with low-pressure refrigerant management in mind: larger-bore piping, purge units to handle non-condensables that enter through near-atmospheric joints, vacuum-rated service procedures.

Fix

For new chiller specification, the low-pressure characteristics of R-1234ze favor systems engineered specifically for it (Trane Chillers using R-1234ze). Retrofitting an existing R-134a chiller to R-1234ze is generally not done — equipment must be designed around the low-pressure operating envelope.

Service problemR-32 (residential AC)

R-32 application sizing — using NBP for evaporator T limit

Scenario · R-32 mini-split design for a hot-and-humid climate where the dew point requires below-freezing evaporator temperatures. Can R-32 reach a 20°F evaporator without going into vacuum?

Saturation property check

R-32 NBP−61.8°Fatmospheric saturation T

R-32 P @ 20°F evap~80 PSIG (positive)well above atmospheric

R-32 P @ −20°F~25 PSIG (still positive)comfortable LT range

OK · R-32 easily handles 20°F evap without vacuum

R-32's low NBP (−62°F) means saturation pressure stays positive across residential AC and even low-temp commercial ranges. At 20°F evaporator, pressure is ~80 PSIG — well into positive-gauge territory. R-32 can comfortably operate across the residential AC and most commercial refrigeration ranges without vacuum management.

Service problemR-407C vs R-410A

Capacity comparison using saturation properties — pressure ratio at design

Scenario · Comparing R-407C and R-410A capacity potential using saturation properties alone. Volumetric capacity is roughly proportional to suction-side density × heat-of-vaporization; for first-order comparison, suction-side pressure (and thus density) is the dominant factor.

Saturation property comparison

R-410A P @ 40°F evap119 PSIGsuction pressure

R-407C P @ 40°F evap (dew)63 PSIGlower suction pressure

Pressure ratio R-410A/R-407C1.89×approximate density ratio

Result · R-410A delivers ~1.5-1.6× capacity per unit compressor displacement vs R-407C

The roughly 2× suction pressure of R-410A vs R-407C translates to approximately 50-60% more volumetric capacity per unit compressor displacement (after accounting for compression ratio and heat-of-vaporization differences). This is why R-22 retrofit to R-410A wasn't a drop-in: smaller-displacement R-410A compressors deliver the same capacity as larger R-22 equipment, but the equipment needs to be sized for R-410A from the start.

Fix

For detailed capacity comparison, do full thermodynamic cycle calculation using CoolProp (Python or WASM): compute h_1 and h_2 at suction and discharge, subtract for refrigerating effect, multiply by mass flow rate. The saturation property comparison here is a first-order proxy — useful for screening but not a substitute for cycle modeling.

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 of Refrigeration 2022 — Chapter 1 (vapor-compression cycle), Chapter 7 (lubricants), Chapter 23 (service procedures). Phase diagram explanations, saturation property usage in cycle calculations.
NIST WebBook — chemical properties, molar masses, CAS registry references.
Manufacturer technical datasheets— Honeywell, Chemours, Arkema, AGC saturation tables for 11 manufacturer-blend refrigerants not in CoolProp's reference library.

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 — saturation doesn't exist; the calculator returns 'transcritical'.
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: ~0.7°F (near-azeotropic) Critical T: 160.5°F Critical P: 712.8 PSIA (698.1 PSIG) NBP: −60.0°F Molar mass: 72.59 g/mol R-407C at 70°F: Bubble pressure: 140.5 PSIG Dew pressure: 117.3 PSIG Glide: ~11°F (significant zeotrope) Critical T: 187.0°F Critical P: 689.4 PSIA NBP: −47.4°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 ~0.7°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 about density, enthalpy, and entropy?

Liquid density, vapor density, and enthalpy of vaporization come from CoolProp for pure refrigerants and predefined blends, but require an extension to the data generator that isn't shipped yet. For now, use the refrigerant's detail page to find its CoolProp identifier, then query CoolProp directly (Python or via the JS WASM wrapper). The data shown here covers saturation P-T and reference properties (critical point, normal boiling point, molar mass).

›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-744 NBP = −108°F, R-32 NBP = −62°F, R-410A NBP = −60°F) work for AC and commercial refrigeration. 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.