About
Pick the refrigerant, enter the pressure and the line temperature, read the answer. Subcool is the calculator an HVAC technician actually reaches for at the unit, and the part that matters most is free forever. Superheat is measured against the dew point and subcooling against the bubble point. On a blend like R-407C those sit more than twelve degrees apart, so an app that quietly uses the average column is wrong in both directions at once. Subcool knows which curve each measurement belongs to and picks it for you, then names the manufacturer's chart the number came from. New residential systems in the United States moved to A2L refrigerants in January 2026 and the pressures are not the ones anyone learned on, so all fifteen refrigerants are free, R-454B and R-32 included, along with superheat, subcooling, target superheat, delta T, airflow and the electrical checks. No counter, no daily limit, no trial that runs out. Subcool Pro adds the engineering side and the paperwork: duct sizing at any friction rate with real velocity and a size a sheet metal shop can cut, total external static against what the air handler is rated for, full psychrometrics from the ASHRAE equations with altitude correction, gas meter clocking and temperature rise against the data plate, and every visit filed against the machine so you can hand the customer a PDF with your company on it. It computes. It does not certify, and it says so on every result. There is no account, no analytics and no networking code in the app at all: your customers and your job records stay on your iPhone.
Features
- Superheat off the dew point, subcooling off the bubble point, picked for you
- Fifteen refrigerants from the manufacturers' own published charts
- R-454B and R-32 for the A2L changeover, free like all the rest
- Target superheat, delta T, airflow and CFM per ton
- Capacitor microfarads, three phase power and voltage imbalance
- Pro: duct sizing from Colebrook-White, not a scanned wheel
- Pro: full psychrometrics with altitude correction
- Pro: clock the meter, check the rise against the data plate
- Pro: every visit filed against the machine, exported as a PDF and a CSV
- Imperial and metric throughout. One payment, never a subscription
- No account, no analytics, no network. Everything stays on your iPhone