Refrigerant Charge & Line-Set Calculator
How much extra refrigerant does a longer line set need? Worked out from the pipe bore and the refrigerant’s own liquid density, not one flat number — so it is right for R-32 and R-454B too, on any liquid-line size.
The system
It is on the outdoor unit nameplate
Advanced / Custom Input — the refrigerant
Filled in from the refrigerant. Quoted at 100 °F / 38 °C.
kg/m³
The line set
The thin one. The fat suction line does not count.
Measure the copper, not the straight-line distance
ft
Between the indoor and outdoor units
ft
Advanced / Custom Input — the pipe
Filled in from the size above, ASTM B280 Type L.
in
From the install manual. Used for the warning only.
ft
ft
What the factory already put in
Stamped on the outdoor unit
lb
Usually 15 ft, sometimes 25 — check the nameplate
ft
Advanced / Custom Input — extra adders
Some manuals list one for a mismatched or larger coil.
oz
oz
From the manufacturer’s own long-line table. Leave at 0 to use the computed one.
oz/ft
Result
Put in the refrigerant, the line set and the nameplate charge, then press “Work out the charge”.
Estimate only — the unit nameplate and the manufacturer’s own long-line table win over this calculation. Charge by weight, then verify with superheat and subcooling once the system has settled.