Refrigerant calculators

The refrigerant side is what techs actually charge for on a service call. Five tools here cover the everyday work: pressure-temperature lookups across five common refrigerants, target superheat for fixed-orifice systems, target subcooling for TXV and EEV systems, total charge calculation for the installed line set length, and delta-T as a diagnostic to combine airflow with capacity.

R-454B is the new A2L refrigerant rolling out across residential split systems and heat pumps in 2025 and 2026 as the R-410A phase-down accelerates. R-454B has a roughly 1.1-degree-Fahrenheit temperature glide between bubble and dew points, which means superheat and subcooling have to reference different saturation values. The PT chart and the superheat/subcooling tools here handle bubble and dew separately so the answer is correct on a glide blend. R-32 (also A2L, near-zero glide) is the other replacement showing up on Daikin and Mitsubishi mini-split systems.

The superheat calculator uses indoor wet bulb and outdoor dry bulb to pull the manufacturer target charge curve, which is the only way to charge a fixed-orifice system correctly on a high-humidity day. Subcooling on a TXV system goes by the nameplate value (usually 8 to 12 degrees) and uses bubble point as the reference. Get the wrong saturation reference on a glide blend and you can be 6 degrees off on the charge target without knowing it.

Delta-T is the airflow-side diagnostic that gets misused constantly. A 20-degree split sounds good but tells you nothing without knowing the return wet bulb. The delta-T tool here pulls the correct target split from the return wet bulb (via the Magnus formula on dry bulb and humidity) and gives a diagnostic readout that combines the airflow side with superheat and static pressure for a real troubleshooting matrix.