Superheat & Subcooling Calculator
Type in your four readings. Superheat and subcooling update as you type.
How it works
Superheat = suction line temp − evaporator saturation temp
Subcooling = condenser saturation temp − liquid line temp
Saturation temperatures come from your gauge pressures and the PT chart for the refrigerant in the system. Most digital manifolds show them directly. Take line temperatures with a pipe clamp on clean, bare copper near the service valves, insulated from outdoor air.
Which number do I charge by?
- TXV or EEV systems: charge by subcooling, to the target on the manufacturer's data plate or charging chart.
- Fixed orifice (piston or cap tube): charge by superheat, to the target for current conditions. Use the target superheat calculator.
Before judging the charge, confirm indoor airflow and let the system run at least 10–15 minutes to settle.
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Results are estimates for field reference. Always confirm against the equipment manufacturer's charging chart, installation instructions and local code. Found a problem with this tool? Tell us.