Offline
No internet, no account required.
ASHRAE
Validated against the standard.
PDF export
Pro-only. Generate professional reports.
$2.99 Pro
Lifetime unlock. No subscriptions.
How it works
Enter your values
Type in your inputs — the app fills code tables and constants for you, so there's nothing to look up.
Get a code-checked result
Instant answer with a clear PASS / FAIL and the exact ASHRAE reference behind every number.
Save & export
Keep a history of calculations and export a clean PDF report to share or attach to a permit (Pro).
What this calculator does
Superheat and subcooling are the two numbers that tell you what is happening inside a refrigeration circuit. This app calculates both from your gauge pressures and line temperatures, so you can diagnose charge, airflow, and metering problems quickly.
The definitions
- Superheat = suction line temperature − suction saturation temperature. Measured on the low side; low superheat risks liquid floodback to the compressor.
- Subcooling = liquid saturation temperature − liquid line temperature. Measured on the high side; it confirms the condenser is fully condensing the refrigerant.
Worked example
Suction pressure converts to a 40°F saturation temperature and the suction line measures 52°F → superheat = 52 − 40 = 12°F.
Liquid saturation is 100°F and the liquid line measures 90°F → subcooling = 100 − 90 = 10°F. Both in a typical healthy range.
Related calculators
Pair it with the refrigerant PT chart and the refrigerant charge calculator.
Superheat and subcooling FAQ
What is the difference between the two?
Superheat is measured on the suction (low) side and shows how much the vapor has warmed past its boiling point; subcooling is measured on the liquid (high) side and shows how far the liquid has cooled below its condensing point.
What are typical target values?
Targets depend on the system and conditions, but many TXV systems aim for roughly 10–12°F of subcooling, while fixed-orifice superheat is set from a charging chart based on indoor and outdoor conditions.
Why does it matter?
Low superheat risks liquid returning to the compressor, while high superheat signals an undercharge or restriction. Subcooling confirms charge and condenser performance.
Does it work offline?
Yes, it runs 100% offline with no account. Free with rewarded ads; a one-time $2.99 Pro unlock adds PDF export and saved history.
Get Superheat Subcool on your phone
Free with rewarded ads · $2.99 lifetime Pro · iOS & Android. Works 100% offline on the job site.