Pick a refrigerant to see its full pressure–temperature (PT) chart, or type a temperature or gauge reading to get the matching saturation pressure or temperature. Blends with glide show both bubble (liquid) and dew (vapor) values.
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0 = sea level, 14.696 psi atmosphere
Enter your values to see the result.
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How to use the Refrigerant Pressure Temperature Chart
Choose the refrigerant printed on the unit's nameplate.
Pick the lookup direction: temperature to pressure, or a gauge reading to saturation temperature.
Set the units (°F/°C and psig, bar or kPa) and, if you work at altitude, enter the elevation.
Type the value to see the saturation pressure or temperature instantly.
Scroll down for the complete PT chart and curve, and download it as CSV for the truck.
How to use a PT chart for superheat and subcooling
A refrigerant only sits at its saturation temperature where liquid and vapor are present together: inside the evaporator and condenser. That lets a pressure gauge act as a thermometer for those coils:
Superheat = suction line temperature − saturation temperature at suction pressure (use the dew point for blends).
Subcooling = saturation temperature at liquid line pressure − liquid line temperature (use the bubble point for blends).
Example: an R-410A system shows 118 psig on the suction gauge, which is about 40 °F on the chart. With the suction line at 50 °F, the superheat is 10 °F.
Quick comparison at common temperatures (psig, sea level)
Temp
R-410A
R-32
R-454B*
R-22
R-134a
R-404A*
-20 °F (-28.9 °C)
26.6
26.6
25.1
10.2
-1.8
17.7
0 °F (-17.8 °C)
48.6
49.2
46.5
23.9
6.5
34.9
20 °F (-6.7 °C)
78.8
80.2
75.8
42.8
18.4
58.3
40 °F (4.4 °C)
118.9
121.6
114.6
68.2
35.0
89.3
60 °F (15.6 °C)
170.7
175.3
164.8
101.1
57.4
129.3
80 °F (26.7 °C)
236.4
243.7
228.2
143.2
86.7
179.8
100 °F (37.8 °C)
318.1
329.0
307.0
195.6
124.1
242.6
120 °F (48.9 °C)
418.3
433.8
403.2
260.1
171.1
319.4
* Blends shown at the bubble (liquid) point. Negative values are below atmospheric pressure (vacuum).
Refrigerant notes
R-410A runs at roughly 1.6 times the pressure of R-22, so gauges, hoses and recovery equipment must be rated for it.
R-454B and R-32 are mildly flammable (A2L) refrigerants used in new air conditioners and heat pumps; R-454B pressures are a few percent below R-410A.
R-22 is no longer produced for servicing in the US; existing systems use reclaimed or stockpiled refrigerant.
R-744 (CO₂) has a critical point of only 87.8 °F (31 °C), so above that a system runs transcritical and no saturation pressure exists.
Never mix refrigerants or charge a different refrigerant than the one on the nameplate; follow EPA Section 608 rules for handling and recovery.
Frequently asked questions
What is a refrigerant PT chart?
A pressure–temperature (PT) chart lists the saturation pressure of a refrigerant at each temperature, the point where liquid and vapor coexist and the refrigerant boils or condenses. Technicians read the gauge pressure, convert it to saturation temperature with the chart, then compare it with the measured line temperature to find superheat and subcooling.
What pressure should R-410A be at 40 °F?
At a 40 °F saturation temperature, R-410A is at about 118 to 119 psig at sea level. A typical comfort-cooling evaporator runs near that temperature, so suction pressures around 110 to 130 psig are common, depending on indoor load and airflow.
What are bubble point and dew point?
Zeotropic blends such as R-407C, R-404A and R-454B boil over a temperature range called glide. The bubble point is the temperature where liquid begins to boil (use it on the liquid line for subcooling); the dew point is where the last liquid evaporates (use it on the suction line for superheat). R-410A's glide is so small that one value is used.
Why are gauge readings different at high altitude?
Gauges read pressure above the local atmosphere. At 5,000 ft the atmosphere is about 12.2 psia instead of 14.7, so the same absolute pressure reads about 2.5 psi higher on the gauge. Enter your altitude so the chart converts gauge values correctly.
How accurate is this PT chart?
The values come from saturation data for each refrigerant interpolated in log pressure, and typically agree with manufacturers' PT charts within about 0.5% (roughly 1 psi at normal operating pressures). Always use the equipment manufacturer's charging chart and instructions as the final reference.
Can I tell the refrigerant charge from pressure alone?
No. Pressure only tells you the saturation temperature. To judge charge you also need the line temperatures to calculate superheat and subcooling, plus indoor and outdoor conditions. Use the superheat and subcooling calculator with the readings from this chart.
What does inHg vac mean?
Below 0 psig the pressure is less than atmospheric, so gauges show vacuum in inches of mercury (inHg). For example, R-134a at −20 °F is about 3.7 inHg vacuum. 1 psi equals about 2.036 inHg.
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