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
This app helps you verify and adjust refrigerant charge using the two field methods technicians rely on: superheat for fixed-orifice systems and subcooling for TXV systems. Correct charge protects the compressor and delivers rated capacity and efficiency.
Which method to use
- Fixed orifice / piston — charge by target superheat, which the app derives from indoor wet-bulb and outdoor dry-bulb conditions.
- TXV / EEV — charge by subcooling to the value on the equipment data plate (often around 10–12°F).
- Line-set length — adjust the factory charge for line length beyond the standard run.
Worked example
On a TXV system with a target of 10°F subcooling: if the liquid line saturation temperature (from the PT chart) is 100°F and the measured liquid line temperature is 88°F, subcooling = 100 − 88 = 12°F — slightly high, so you would recover a little charge.
Related calculators
Read saturation temperatures with the refrigerant PT chart and confirm readings with the superheat and subcooling calculator.
Refrigerant charge FAQ
Superheat or subcooling — which one?
Use the superheat method to charge fixed-orifice (piston) systems and the subcooling method for systems with a TXV or EEV. The app supports both and uses the manufacturer target where available.
Does it support newer refrigerants?
Yes. It includes common refrigerants such as R-410A and R-22 along with newer low-GWP blends like R-454B and R-32, since saturation behavior differs by refrigerant.
Does it adjust for line-set length?
Yes. You can add charge for line lengths beyond the standard factory run, following the per-foot adjustment the equipment specifies.
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 Refrigerant Charge on your phone
Free with rewarded ads · $2.99 lifetime Pro · iOS & Android. Works 100% offline on the job site.