Calculate subcooling or look up pressure
Quick example: R-410A at 341.9 psig is about 105°F saturated-liquid temperature. A 95°F liquid-line reading gives 10°F actual subcooling. A manufacturer target must be checked separately.
Your field reading
Select the refrigerant and enter liquid-side measurements
The interactive calculator is loading. The 10°F example shown below and the pressure–temperature chart remain available without JavaScript.
Pressure lookup uses the selected refrigerant’s bubble (liquid) PT values, from −40°F to 150°F. No extrapolation.
Exact 5°F PT checkpoint. The default result is a measured example, not a recommended charge target.
Quick PT reference
R-410A saturated-liquid (bubble) pressures
| Bubble temp | Pressure |
|---|---|
| 201.8 psig | |
| 255.4 psig | |
| 296.4 psig | |
| 341.9 psig | |
| 392.3 psig | |
| 447.9 psig |
Tap a row to use that temperature’s pressure in the calculator. For refrigerant blends, bubble is for liquid subcooling; dew is for vapor superheat.
Actual ≠ target: a PT/subcooling reading alone does not authorize charging. Use the exact equipment manufacturer’s charging procedure, target and tolerances. A fixed-orifice system may require target superheat instead.
R-410A Pressure–Temperature and Subcooling Chart
39 saturation checkpoints · −40°F to 150°F in 5°F increments
Read the liquid-side saturation bubble temperature and its corresponding gauge pressure. The final column illustrates the liquid-line temperature that would be 10°F below saturation—it is not a recommended target. The calculator above works between the listed rows by bounded linear interpolation.
| Bubble °F | Bubble °C | Pressure psig | kPa(g) | Liquid line if 10°F lower |
|---|---|---|---|---|
| -40°F | -40.0°C | 10.8 | 74 | -50.0°F |
| -35°F | -37.2°C | 14.1 | 97 | -45.0°F |
| -30°F | -34.4°C | 17.8 | 123 | -40.0°F |
| -25°F | -31.7°C | 21.9 | 151 | -35.0°F |
| -20°F | -28.9°C | 26.3 | 181 | -30.0°F |
| -15°F | -26.1°C | 31.2 | 215 | -25.0°F |
| -10°F | -23.3°C | 36.5 | 252 | -20.0°F |
| -5°F | -20.6°C | 42.2 | 291 | -15.0°F |
| 0°F | -17.8°C | 48.4 | 334 | -10.0°F |
| 5°F | -15.0°C | 55.2 | 381 | -5.0°F |
| 10°F | -12.2°C | 62.4 | 430 | 0.0°F |
| 15°F | -9.4°C | 70.3 | 485 | 5.0°F |
| 20°F | -6.7°C | 78.7 | 543 | 10.0°F |
| 25°F | -3.9°C | 87.7 | 605 | 15.0°F |
| 30°F | -1.1°C | 97.4 | 672 | 20.0°F |
| 35°F | 1.7°C | 107.7 | 743 | 25.0°F |
| 40°F | 4.4°C | 118.8 | 819 | 30.0°F |
| 45°F | 7.2°C | 130.6 | 900 | 35.0°F |
| 50°F | 10.0°C | 143.2 | 987 | 40.0°F |
| 55°F | 12.8°C | 156.5 | 1079 | 45.0°F |
| 60°F | 15.6°C | 170.7 | 1177 | 50.0°F |
| 65°F | 18.3°C | 185.8 | 1281 | 55.0°F |
| 70°F | 21.1°C | 201.8 | 1391 | 60.0°F |
| 75°F | 23.9°C | 218.7 | 1508 | 65.0°F |
| 80°F | 26.7°C | 236.5 | 1631 | 70.0°F |
| 85°F | 29.4°C | 255.4 | 1761 | 75.0°F |
| 90°F | 32.2°C | 275.4 | 1899 | 80.0°F |
| 95°F | 35.0°C | 296.4 | 2044 | 85.0°F |
| 100°F | 37.8°C | 318.6 | 2197 | 90.0°F |
| 105°F | 40.6°C | 341.9 | 2357 | 95.0°F |
| 110°F | 43.3°C | 366.4 | 2526 | 100.0°F |
| 115°F | 46.1°C | 392.3 | 2705 | 105.0°F |
| 120°F | 48.9°C | 419.4 | 2892 | 110.0°F |
| 125°F | 51.7°C | 447.9 | 3088 | 115.0°F |
| 130°F | 54.4°C | 477.9 | 3295 | 120.0°F |
| 135°F | 57.2°C | 509.4 | 3512 | 125.0°F |
| 140°F | 60.0°C | 542.5 | 3740 | 130.0°F |
| 145°F | 62.8°C | 577.3 | 3980 | 135.0°F |
| 150°F | 65.6°C | 613.9 | 4233 | 140.0°F |
If the input is not a displayed 5°F source row, the calculator interpolates within the PT range. Pressure is gauge pressure (psig or kPa gauge), not absolute psia. Do not use these references for equipment safety-limit determination or as charging instructions.
Selected refrigerant saturation curve
R-410A · Bubble temperature versus psigCurve is a visualization of the same source checkpoints, not a separate prediction model.
What should subcooling be?
There is no universal subcooling target for every R-410A, R-454B or other refrigeration system. In air-conditioning equipment using a thermostatic expansion valve (TXV) or electronic expansion valve (EEV), the manufacturer often provides a target subcooling and permissible tolerance on the nameplate or in its charging instructions. The right number may vary with model, indoor/outdoor conditions, line length, or cooling/heating operating mode.
TXV / EEV equipment
Subcooling is often the manufacturer-prescribed charge verification method. Measure actual subcooling, then compare against the model-specific published target under permitted conditions.
Fixed orifice / piston
Many fixed-orifice air conditioners are charged using an OEM target-superheat chart based on operating conditions. A single subcooling target is not an adequate substitute.
When an OEM target is entered into the calculator, its difference is calculated as actual minus target. Positive means above your entered number; negative means below. Neither result, on its own, establishes the cause or authorizes adding or removing refrigerant.
Where and how to measure subcooling
- Identify the refrigerant and system. Check nameplate, metering device and cooling/heating mode.
- Confirm stable OEM charging conditions. Check airflow, load, equipment instructions and any permitted ambient-temperature range.
- Record high-side liquid pressure. Use the specified service port and correct gauge-pressure units.
- Clamp the liquid line. Measure actual line temperature at the manufacturer’s specified location with good thermal contact.
- Convert pressure to bubble saturation temperature. Use the correct refrigerant, especially for gliding blends.
- Subtract line temperature. Compare the resulting actual subcooling with the OEM target only when the method and test conditions apply.
Subcooling formula and worked examples
Actual liquid subcooling is the temperature difference between the saturated-liquid bubble temperature at the measured liquid pressure and the measured liquid-line temperature:
Subcooling = Bubble saturation temperature − Liquid-line temperature
Example: R-410A
At 341.9 psig (about 105°F saturated liquid), a 95°F liquid line gives 105 − 95 = 10°F actual subcooling. The value is a measurement; compare with the actual equipment target.
Example: R-454B blend
R-454B has different bubble and dew pressures. The liquid-side lookup uses the bubble curve; selecting the dew curve would give the wrong result. Use R-454B data for R-454B equipment.
What low, high or negative subcooling means
Higher- or lower-than-target subcooling may be associated with charge, heat rejection, liquid restrictions, metering conditions, or measurement error. Check the full system instead of making a one-number diagnosis. A negative calculated value means the measured line is warmer than the selected bubble saturation temperature; recheck gauge readings, sensor placement, refrigerant and operating state before interpreting the result.
Source data, limitations and calculation method
The pressure–temperature points used by the interactive tool are the same manufacturer-reference checkpoints used on Turn2Engineering’s Refrigerant Pressure Temperature Chart, not the uploaded page’s older R-410A-only data. For R-454B, R-404A and R-407C, the saturated-liquid/bubble values are used. Interpolation is linear and restricted to adjacent 5°F points; results between rows are approximate.
- Arkema Forane Refrigerants Technical Digest — saturation pressure references for R-410A, R-32, R-22, R-134a, R-404A and R-407C.
- Chemours Opteon XL41 (R-454B) thermodynamic properties — liquid/bubble and vapor/dew saturation state reference.
- Lennox R-454B charging procedure — equipment-specific use of saturation temperature, liquid-line temperature and target comparison.
- Turn2Engineering Refrigerant Pressure Temperature Chart — companion full refrigerant comparison and data basis.
Not included: an OEM-approved target chart, a refrigerant charge recommendation, operation beyond the displayed PT range, or an equipment safety approval. This tool is a reference for trained HVAC/R users, not a substitute for applicable procedures and regulated service requirements.
Subcooling Chart FAQs
How do you calculate subcooling from high-side pressure?
Identify the actual refrigerant, convert measured liquid-side pressure to the saturated-liquid/bubble temperature, then subtract measured liquid-line temperature. A 105°F saturation and 95°F line reading produce 10°F subcooling.
Should subcooling be 10°F or 12°F?
Those values sometimes appear in examples, but the right target comes from the manufacturer for your exact equipment and operating conditions. Neither 10°F nor 12°F is universally correct.
Do I use bubble or dew pressure for R-454B and R-407C?
Use bubble/saturated-liquid data for liquid-line subcooling. Dew/saturated-vapor data are used for vapor superheat, unless the equipment manufacturer’s procedure explicitly specifies a different reference.
Does a TXV system use subcooling or superheat to verify charge?
Many TXV/EEV air-conditioning systems use the manufacturer-prescribed subcooling method for charge verification, while the valve regulates evaporator superheat. Always use the actual equipment instructions.
Does a low subcooling result prove undercharge?
No. A single measurement cannot establish cause. Recheck measurement location, load, airflow, condensing conditions, restrictions and service procedure before drawing a conclusion.
What is the difference between psig and psia?
Psig is pressure relative to local atmospheric pressure; psia is absolute pressure. This field chart displays gauge pressure. Do not insert absolute pressure readings into a gauge-pressure input without converting them appropriately.
Turn2Engineering | Subcooling Chart | Gauge-pressure saturation references and independently calculated subcooling differences.