Refrigerant Charge Calculator

The Refrigerant Charge Calculator computes superheat and subcooling from measured pressures and temperatures for R410A, R22, R134a, R32, and R404A. It includes an interactive SVG P-T saturation curve, target range indicators, and diagnostic guidance for system charging — free, no signup required.

Measurement Input

Refrigerant Type

Suction Pressure (psig)

Suction Line Temperature (°F)

Liquid/Discharge Pressure (psig)

Liquid Line Temperature (°F)

P-T Saturation Chart — R-410A

Refrigerant Reference

Refrigerant Type	Type	Target Superheat	Target Subcooling	GWP	ODP
R-410A	HFC blend	8-14°F	10-18°F	2088	0
R-22	HCFC	10-15°F	10-15°F	1810	0.055
R-134a	HFC	8-12°F	10-15°F	1430	0
R-32	HFC	5-10°F	5-10°F	675	0
R-404A	HFC blend	10-15°F	10-15°F	3922	0

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What is Refrigerant Charging?

Refrigerant charging is the process of adding or removing refrigerant to achieve optimal system performance. Superheat (measured suction temperature minus saturation temperature at suction pressure) indicates how much vapor is heated beyond the boiling point — target is 8–14 °F for TXV systems. Subcooling (saturation temperature at liquid pressure minus measured liquid temperature) shows how much liquid is cooled below the condensing point — target is 10–18 °F. Low superheat suggests overcharge or flooding; high superheat indicates undercharge or restricted flow.

How to Use This Calculator

Select the refrigerant type used in your system (R410A, R22, R134a, R32, or R404A)
Measure and enter the suction pressure (psig) and suction line temperature (°F) at the compressor inlet
Measure and enter the liquid/discharge pressure (psig) and liquid line temperature (°F) at the condenser outlet
Click Calculate to see superheat, subcooling, and system diagnosis
Review the P-T chart visualization to see operating points relative to the saturation curve

Frequently Asked Questions

What is the correct superheat for an air conditioner?

For systems with a thermostatic expansion valve (TXV/TEV), target superheat is 8–14 °F (4–8 °C). For fixed-orifice systems, superheat should be 10–20 °F depending on indoor/outdoor conditions. High superheat means the evaporator is starved for refrigerant; low superheat means liquid may reach the compressor (risk of slugging).

What is the difference between superheat and subcooling?

Superheat is measured at the evaporator outlet (low-pressure side) and indicates how much the gas is heated above its boiling point. Subcooling is measured at the condenser outlet (high-pressure side) and indicates how much the liquid is cooled below its condensation point. Both values together diagnose system charge level and performance.

Why has R22 been phased out?

R22 (Freon) is an HCFC refrigerant with an ozone depletion potential (ODP) of 0.055 and a global warming potential (GWP) of 1,810. Under the Montreal Protocol, R22 production was phased out in 2020 in developed countries. R410A (GWP 2,088) is the common replacement, though newer low-GWP alternatives like R32 (GWP 675) are gaining adoption.