Refrigerant PT Calculator (Pressure ↔ Temperature)
By BRIX Editorial Team · Updated
A refrigerant PT calculator converts a gauge pressure into the refrigerant's saturation temperature, or a temperature into its saturation pressure. For example, R-454B at 118 psig has a dew point of 44.9°F and a bubble point of 42.1°F. This one covers R-410A, R-454B, R-32 and R-22 and corrects for altitude.
- Bubble point (use for subcooling)
- 42.1°F
- Temperature glide
- 2.7°F
- Altitude correction
- −0.0 psi
- Pressure on the sea-level chart
- 118.0 psig
At 118.0 psig, R-454B starts boiling at 42.1°F and finishes at 44.9°F. Use the dew point for superheat and the bubble point for subcooling. Reference only: follow the manufacturer's charging chart.
Key takeaways
- Pressure → temperature tells you where the refrigerant is boiling or condensing; that's the starting point for superheat and subcooling.
- Blends return two answers: dew point for the suction side, bubble point for the liquid side.
- At 5,000 ft a gauge reads about 2.5 psi higher than a sea-level PT chart for the same saturation temperature.
- Values are interpolated from PT tables computed with CoolProp 8.0.0 and checked against published Daikin and Arkema charts.
How does a refrigerant PT calculator work?
It looks up the refrigerant's saturation curve, the pressure at which liquid and vapor coexist at each temperature, and interpolates between rows. Our tables run from −40°F to 150°F in 5°F steps; between rows the calculator interpolates linearly. If you enter an altitude, it first converts your gauge reading to the sea-level basis the chart uses.
Chart psig = Gauge psig − (14.696 − Local atmospheric psia); Saturation temp = PT table(Chart psig)
- 14.696 psia
- standard sea-level atmosphere, the zero for printed PT charts
- Local atmospheric psia
- standard atmosphere at your altitude (NASA Glenn model)
- PT table
- dew column for superheat, bubble column for subcooling on blends
- 1
Pick the refrigerant.
Use the one on the nameplate. The four charts give different answers for the same pressure.
- 2
Choose the direction.
Pressure → temperature for gauge readings; temperature → pressure to know what the gauge should show.
- 3
Enter the value and altitude.
Leave altitude at 0 near sea level. Above a couple thousand feet the correction starts to matter.
- 4
Use the right result.
On blends, dew point for superheat and bubble point for subcooling. Pure refrigerants give one answer.
How much does altitude change a gauge reading?
| Altitude (ft) | Atmosphere (psia) | Gauge reads high by (psi) |
|---|---|---|
| 0 | 14.7 | +0.0 |
| 1,000 | 14.2 | +0.5 |
| 2,500 | 13.4 | +1.3 |
| 5,000 | 12.2 | +2.5 |
| 7,500 | 11.1 | +3.6 |
| 10,000 | 10.1 | +4.6 |
A psi or two hardly matters at condensing pressures, but on the suction side of an R-22 system, or any refrigerant at low evaporator temperatures, it shifts saturation temperature enough to change a superheat reading by a degree or more.
Bubble point vs. dew point
Blends like R-454B boil over a range of temperatures at one pressure. The bubble point is where boiling starts (saturated liquid) and the dew point is where it ends (saturated vapor). The calculator shows both, plus the glide between them. R-454B has about 2.7°F of glide at 118 psig; R-410A, about 0.2°F; R-32 and R-22, none.
Common PT lookup mistakes
- Wrong refrigerant. R-32 and R-410A are only a few psi apart, so the wrong chart gives an answer that looks believable. Check the nameplate.
- Wrong column on a blend. Dew for suction-side readings, bubble for liquid-side readings.
- Mixing up gauge and absolute pressure. Field charts are psig. Add 14.696 only if a spec sheet asks for psia.
- Treating saturation pressure as a target. It tells you where the refrigerant boils, not whether the charge is right.
Frequently asked questions
How do I convert refrigerant pressure to temperature?
Find the refrigerant's PT chart, locate the gauge pressure and read the saturation temperature on that row, interpolating between rows. On blends, read the dew column for suction readings and the bubble column for liquid readings. This calculator does the lookup and interpolation for you.
Is the PT relationship different at altitude?
The refrigerant's absolute pressure at a given temperature doesn't change, but a gauge reads relative to local air pressure. At altitude the air is thinner, so the gauge shows a higher number than a sea-level chart. Subtract the difference before looking up the temperature.
Why does the calculator give two temperatures?
For blends with glide, such as R-454B, the refrigerant starts boiling at the bubble point and finishes at the dew point. Use the dew point for superheat and the bubble point for subcooling. Pure refrigerants like R-32 and R-22 give one temperature.
How accurate are these values?
They come from tables computed with CoolProp 8.0.0 that match the Daikin and Arkema charts within 0.1 psi for R-22, R-32 and R-410A and within 1.5% for R-454B. Between 5°F rows the calculator interpolates linearly, which adds very little error over that span.
Can I use this for R-134a or R-404A?
Not yet. It covers R-410A, R-454B, R-32 and R-22. Use the refrigerant manufacturer's chart for anything else, and never substitute one refrigerant's chart for another's.
Related
- Refrigerant PT Charts (Pressure-Temperature)Refrigerant pressure-temperature charts for R-410A, R-454B, R-32 and R-22, computed with CoolProp, plus a side-by-side comparison and how to read them.
- R-410A PT Chart (Pressure-Temperature)R-410A pressure-temperature chart from −40°F to 150°F in psig, computed with CoolProp, plus a quick lookup and what the 2026 EPA rule change means.
- R-454B PT Chart (Pressure-Temperature)R-454B pressure-temperature chart from −40°F to 150°F with bubble (liquid) and dew (vapor) psig, a quick lookup, °F/°C toggle and how to read glide.
- R-32 PT Chart (Pressure-Temperature)R-32 pressure-temperature chart, −40°F to 150°F in psig, one column because R-32 is a pure refrigerant. A2L safety notes, GWP 675 and a PT lookup.
- R-22 PT Chart (Pressure-Temperature)R-22 pressure-temperature chart from −40°F to 150°F in psig, plus where R-22 stands after EPA ended production in 2020 and what retrofits require.
- Superheat CalculatorFree superheat calculator: enter suction pressure and suction line temperature for R-410A, R-454B, R-32 or R-22 and compare with your target superheat.
- Subcooling CalculatorFree subcooling calculator: enter liquid line pressure and temperature for R-410A, R-454B, R-32 or R-22, using the bubble column, and check against target.
- Superheat and Subcooling, Explained with Worked ExamplesSuperheat and subcooling explained with worked R-454B and R-32 examples: which PT column to use, the formulas, common mistakes and five check questions.
- HVAC Software That Answers the Phone, Books the Tech and Keeps the BooksHVAC software that answers every no-heat and no-cool call, books the tech, follows up on replacement quotes, chases invoices and keeps QuickBooks clean.
- BTU CalculatorFree BTU calculator built on the ENERGY STAR room AC sizing chart, with sun, occupant and kitchen adjustments. A rule of thumb, not a Manual J load calc.
Sources
- CoolProp 8.0.0: thermophysical property library, used to compute the PT tables (checked October 24, 2026)
- Daikin Comfort Technologies: A1 vs. A2L Pressure Temperature Chart, USA (PM-A2LPTC-USA_04-24), used to check the tables (checked October 24, 2026)
- NASA Glenn Research Center: Earth Atmosphere Model (troposphere pressure curve fit) (checked October 24, 2026)