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Log refrigerant used per job to track remaining cylinder weight over time.
How to Use the Refrigerant Cylinder Calculator
Select the refrigerant and switch between pounds and kilograms to match your scale and cylinder label.
Enter the tare weight stamped on the cylinder collar and the current gross weight from a calibrated scale, with the valve closed and no hoses attached.
Enter the full capacity for percent remaining, the refrigerant the job needs, and the water capacity stamped on a recovery cylinder for its fill limit.
Press Calculate Remaining, then log the refrigerant used on each job to keep a running total.
How to check the refrigerant left in a cylinder
A cylinder of refrigerant holds liquid and vapour at the same time, so neither the gauge nor the feel of the cylinder tells you how much is left. Weight does. The calculator turns two weighings into the net refrigerant, the percent of a full cylinder, whether it covers the next job, and, for a recovery cylinder, how much more it can safely take.
Net weight and tare weight
Net refrigerant is the gross weight on the scale minus the tare weight of the empty cylinder. Use the tare stamped on the collar of that cylinder, because tare varies between makers and between batches of the same size. A tare error goes straight into the charge: if the tare is 1 lb too low, the cylinder looks 1 lb emptier than it is, and if it is too high, you may run out mid-charge.
Percent remaining and the job check
Percent remaining compares the net weight with the full capacity on the label. When you enter the refrigerant a job needs, the calculator shows whether the cylinder covers it and what is left afterwards. If the net weight comes out above the stated full capacity, the tare or the scale is wrong, and the calculator flags it. Work out the job requirement itself with the refrigerant charge calculator.
The recovery cylinder fill limit
A recovery cylinder must never be filled liquid-full, because liquid expands as it warms. AHRI Guideline K, a voluntary standard for containers of recovered non-flammable fluorocarbon refrigerants, limits liquid to 80% of the internal volume. The maximum net fill is therefore 0.8 times the water capacity times the specific gravity of the liquid at 25°C. That gives multipliers of 0.85 for R-410A, 0.96 for R-22, 0.97 for R-134a, 0.84 for R-404A and 0.77 for R-32, applied to the stamped water capacity. The specific gravities come from CoolProp saturated liquid densities. Never fill past the limit, and never refill a recovery cylinder with a different refrigerant.
Pounds and kilograms
Labels in Canada appear in both pounds and kilograms, and imported cylinders are often marked in kilograms only. The units selector converts every field and every result, so you can weigh in one unit and read the other. For other refrigerant quantities, the refrigerant unit converter handles mass and pressure units. One pound is 0.4536 kg.
Weighing accurately in the field
Use a calibrated refrigerant scale and weigh with the valve closed and the hoses off, because hose weight inflates the gross reading. Temperature does not change the weight, so the scale reading holds in a hot van, although a very warm cylinder will be at higher pressure and harder to draw liquid from. Keep it in the shade and weigh on a flat, level surface.
Moving cylinders between jobs
Carrying refrigerant cylinders in a vehicle falls under the federal Transportation of Dangerous Goods Regulations. Transport Canada's page on containers explains the container requirements. Secure the cylinders upright, keep valve caps on, and do not carry a cylinder that is over its fill limit.
Recording what you add and recover
Weigh the cylinder before and after each job, and record the difference as the refrigerant added or recovered. The weights go straight onto the service record, and the service report generator gives you a place for them. Rules on records vary by province and by employer, so check what applies to your work.
Frequently Asked Questions
On a recovery or refillable cylinder, the tare weight (TW) is stamped on the collar, next to the water capacity (WC). If a disposable cylinder shows no tare weight, weigh a new sealed cylinder and subtract the net weight on the label. The Example button uses a tare of 18.0 lb and a gross of 33.5 lb, which leaves 15.5 lb, or 62% of a 25 lb cylinder. A 6.5 lb job would leave 9.0 lb.
AHRI Guideline K limits liquid to 80% of the internal volume. Multiply the stamped water capacity by 0.8 and by the specific gravity of the liquid refrigerant at 25°C. For R-410A the specific gravity is 1.062, so a cylinder with a 50 lb water capacity holds at most 42.5 lb of net refrigerant. With a tare of 29.0 lb, stop at a gross weight of 71.5 lb. The Recovery Example button shows this case.
A cylinder holding both liquid and vapour sits at the saturation pressure for its temperature, whatever the amount of liquid. R-410A at 25°C reads about 16.6 bar absolute whether the cylinder is nearly full or nearly empty. The gauge only drops once the liquid is gone, so weight is the only reliable measure of what is left.
Log the refrigerant used on each job in the job tracker. It adds up the total and shows the estimated weight remaining after those jobs, based on the net weight from your last weighing. Weigh the cylinder again after the jobs to confirm the total. Switching units converts the logged jobs as well.