Offline HVAC field calculator with R-454B PT charts, superheat/subcooling, duct sizing, load estimates & psychrometrics. No subscription, no ads, no tracking. Free PT charts (R-454B/R-32/R-410A) + unit converter. Pro: $9.99 one-time for all calculators, 13 refrigerants & PDF export. 100% offline — built for techs on the roof. Feedback welcome!