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Log refrigerant used per job to track remaining cylinder weight over time.
How to check remaining refrigerant in a cylinder on the job
Every refrigerant cylinder has 2 weights stamped or printed on it: the tare weight (TW) and sometimes the full gross weight. Tare weight is the empty cylinder weight. Put the cylinder on a scale, subtract the tare weight, and you have the net refrigerant remaining. That's the entire calculation — this tool just does the subtraction for you and adds percentage-remaining and job-sufficiency checks.
In Canada, technicians working on refrigerant systems are required to track refrigerant use and recovery under Environment and Climate Change Canada's regulations. Knowing your cylinder weight before and after each job keeps your records accurate and prevents running out of refrigerant mid-charge on a job site.
Standard cylinder sizes for Canadian technicians
R-410A is most commonly sold in 25 lb cylinders in Canada, with the empty cylinder (tare) weighing approximately 20-22 lbs. Full gross weight is typically 45-47 lbs. Larger 50 lb cylinders are available from some suppliers. R-32 and R-454B cylinders are often sold in 11 kg (24.3 lb) cylinders as this refrigerant is imported from manufacturers using metric sizing. R-22 reclaimed refrigerant is sold in 30 lb and 50 lb cylinders.
Always use the tare weight stamped on your specific cylinder — tare weight varies between manufacturers and even between cylinders of the same size. Using a generic tare weight instead of the stamped value introduces error into every weight calculation. A 1 lb tare weight error means you could add 1 lb too much or too little refrigerant to every system you charge.
Weighing cylinders accurately in the field
Use a calibrated refrigerant scale — not a bathroom scale or postal scale. Refrigerant scales typically read in 0.1 lb increments and are designed for the weight range of full cylinders. Weigh the cylinder with the valve closed and no hoses or manifold attached. If you weigh with hoses attached, the hose weight inflates your gross reading and makes the cylinder appear to have more refrigerant than it does.
On hot job sites, keep the cylinder in the shade. Refrigerant pressure increases significantly with temperature, but the weight does not change — the scale reading is accurate regardless of cylinder temperature. However, a very hot cylinder in a sunny van may have elevated pressure that makes liquid withdrawal difficult. Use the refrigerant charge calculator to confirm you have enough refrigerant for the job before arriving on site.
Recovery cylinders vs. virgin refrigerant cylinders
Recovery cylinders have a yellow top and grey body by convention, and are rated for a maximum fill level — typically 80% of the water capacity by weight. Never overfill a recovery cylinder. Recovery cylinders also have their own tare weight stamped on the collar. To find how much refrigerant you've recovered: weigh the recovery cylinder before and after, and subtract. The difference is the recovered refrigerant weight. Track this against the expected charge weight to confirm a full recovery.
Frequently Asked Questions
The tare weight is stamped or printed on the cylinder collar, labelled TW. It's given in pounds on North American cylinders. To find remaining refrigerant: weigh the cylinder on a calibrated scale with the valve closed and no hoses attached, then subtract the tare weight. This calculator does that subtraction and shows remaining refrigerant as a percentage of full capacity. Always use the tare weight from your specific cylinder — never use a generic estimate, as tare weights vary between manufacturers and cylinder batches.
A full 25 lb R-410A cylinder typically weighs 43-47 lbs gross, depending on the cylinder manufacturer. The empty cylinder (tare) weighs approximately 20-22 lbs, stamped on the collar. To check remaining refrigerant on a partial cylinder: weigh it, subtract the tare weight stamped on the cylinder, and the result is net refrigerant remaining. This calculator automates that check and also compares the remaining amount to your job's required charge from the refrigerant charge calculator.