# Refrigerant PT Calculator (Pressure ↔ Temperature)

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.

## 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.

> **Reference tool: follow the manufacturer's charging chart**
>
> This converts saturation pressure and temperature. It doesn't tell you whether a charge is right. Targets and charging methods come from the equipment's installation instructions, which take precedence over any generic table or rule of thumb.

## 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.

**Altitude-corrected lookup**

```
Chart psig = Gauge psig − (14.696 − Local atmospheric psia);  Saturation temp = PT table(Chart psig)
```

Where:
- 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.

> **Worked examples (illustrative readings)**
>
> **Blend:** R-454B at 118 psig, sea level. Dew point 44.9°F, bubble point 42.1°F, glide 2.7°F.
>
> **Pure refrigerant:** R-32 at 40°F saturates at 121.0 psig. Liquid and vapor share the number.
>
> **Altitude:** R-410A reads 118 psig at 5,000 ft. Subtract 2.5 psi to get 115.5 psig on the chart: a dew point of **38.7°F**, versus 39.8°F if you ignored the altitude.

## How much does altitude change a gauge reading?

**Standard atmospheric pressure and the gauge offset against a sea-level PT chart**

| 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 |

_Computed from [NASA Glenn's standard-atmosphere model](https://www.grc.nasa.gov/www/k-12/airplane/atmos.html), scaled to 14.696 psia at sea level. Weather moves local pressure by a fraction of a psi on top of this._

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.

### Use the result

- [Superheat calculator](https://www.brix.so/tools/superheat-calculator): Suction pressure and line temperature to superheat.
- [Subcooling calculator](https://www.brix.so/tools/subcooling-calculator): Liquid pressure and line temperature to subcooling.
- [Refrigerant PT charts](https://www.brix.so/reference/refrigerant-pt-chart): Full printable tables for all four refrigerants.

BRIX keeps the office side moving while you're in the field: it answers calls, books jobs on your schedule and texts back anyone you miss.

- [AI receptionist](https://www.brix.so/features/ai-receptionist): Answers every call 24/7, qualifies the caller, books the job and texts back anyone it misses.
- [Scheduling and dispatch](https://www.brix.so/features/scheduling-dispatch): Assigns the right crew to the right job based on skills, location and availability.

## 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)](https://www.brix.so/reference/refrigerant-pt-chart)
- [R-410A PT Chart (Pressure-Temperature)](https://www.brix.so/reference/refrigerant-pt-chart/r-410a)
- [R-454B PT Chart (Pressure-Temperature)](https://www.brix.so/reference/refrigerant-pt-chart/r-454b)
- [R-32 PT Chart (Pressure-Temperature)](https://www.brix.so/reference/refrigerant-pt-chart/r-32)
- [R-22 PT Chart (Pressure-Temperature)](https://www.brix.so/reference/refrigerant-pt-chart/r-22)
- [Superheat Calculator](https://www.brix.so/tools/superheat-calculator)
- [Subcooling Calculator](https://www.brix.so/tools/subcooling-calculator)
- [Superheat and Subcooling, Explained with Worked Examples](https://www.brix.so/academy/hvac/refrigeration/superheat-subcooling)
- [HVAC Software That Answers the Phone, Books the Tech and Keeps the Books](https://www.brix.so/for/hvac)
- [BTU Calculator](https://www.brix.so/tools/btu-calculator)

## Sources

- [CoolProp 8.0.0: thermophysical property library, used to compute the PT tables](https://coolprop.org/coolprop/HighLevelAPI.html) (checked 2026-10-24)
- [Daikin Comfort Technologies: A1 vs. A2L Pressure Temperature Chart, USA (PM-A2LPTC-USA_04-24), used to check the tables](https://www.chadwellsupply.com/globalassets/articles-pk/a2l/a2lptc-usa_04-24.pdf) (checked 2026-10-24)
- [NASA Glenn Research Center: Earth Atmosphere Model (troposphere pressure curve fit)](https://www.grc.nasa.gov/www/k-12/airplane/atmos.html) (checked 2026-10-24)

Talk to BRIX: call or text (518) 588-1122, email eeharris2004@gmail.com, or book a 15-minute call at https://cal.com/ethanharris/15min.

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Written by BRIX Editorial Team. Last updated 2026-10-24.
Canonical: https://www.brix.so/tools/refrigerant-pt-calculator