Superheat & Subcooling Calculator
Superheat and subcooling measurements tell you whether an HVAC system has the correct refrigerant charge. This calculator converts your pressure readings to saturation temperatures and computes both values.
Enter Your Measurements
Results
How to Use This Calculator
- Attach gauges and record suction and liquid line pressures.
- Measure suction line and liquid line temperatures with a clamp thermometer.
- Select your refrigerant type.
- Review superheat and subcooling values.
How Superheat/Subcooling Calculation Works
Refrigerant has a known relationship between pressure and boiling/condensing temperature (the P-T chart). By measuring pressure, we know the saturation temperature. Superheat is how much warmer the suction gas is above its boiling point — it should be 5–15°F. Subcooling is how much cooler the liquid line is below its condensing point — it should be 8–14°F. Values outside these ranges indicate charge problems, airflow issues, or restrictions.
Formula
Superheat = Suction Line Temp − Evaporator Saturation Temp (from P-T chart). Subcooling = Condenser Saturation Temp − Liquid Line Temp.