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Guide 02

How to calculate refrigerant leak rate

EPA defines the leak rate as the percentage of the full charge that would be lost over 12 months if the current rate of loss continued. There are two allowed methods, and one facility must use the same one for all its appliances.

Updated September 2026

Method 1: annualizing

  1. Divide the pounds added to return the appliance to full charge by the full charge.
  2. Divide the number of days since refrigerant was last added (maximum 365) by 365.
  3. Divide the result of step 1 by the result of step 2, then multiply by 100.
leak rate % = (lb added / full charge) / (min(days, 365) / 365) x 100

Example: a 60 lb R-404A walk-in freezer. On August 25 you add 3 lb, and it is the first addition since January 1, 2026, so 365 days are used: 3 / 60 / 1 x 100 = 5.00%. On September 24 you add another 3 lb, 30 days later: 3 / 60 / (30 / 365) x 100 = 60.83%. That is over the 20% commercial refrigeration threshold, so the repair clock starts: repair by October 24.

Method 2: rolling average

  1. Add up all refrigerant added over the previous 365 days, or since the last successful follow-up verification test if that was less than a year ago.
  2. Divide by the full charge and multiply by 100.
leak rate % = (lb added in the window / full charge) x 100

Example: the same 60 lb system with 3 lb in August and 3 lb in September gives 6 / 60 x 100 = 10.00%. Under 20%, no repair required yet. The two methods can give very different answers for the same history, which is why the method is fixed per facility.

The first calculation in 2026

For the first calculation after January 1, 2026 under Part 84, the annualizing method substitutes 365 days, and the rolling average method counts only pounds added since January 1, 2026 (84.106(b)).

When you do not need a calculation

  • Refrigerant added immediately after a retrofit.
  • The charge added when a new appliance is installed.
  • A seasonal variance: refrigerant removed for a change of season and later added back, no more than the amount removed, within 12 months.

Common mistakes

  • Rounding before comparing. The threshold is exceeded only when the rate is above it, so 20.00% on commercial refrigeration does not trigger repair, but 20.01% does.
  • Switching methods between visits. The method can change only when an owner acquires a facility that used a different one, and only if no appliance there exceeds the threshold under either method.
  • Treating a multi-circuit rack as one appliance. Each independent circuit is its own appliance.

Skip the arithmetic with the free leak rate calculator, which uses exactly these formulas.

Refrigerant leak rate calculatorEnter the top-offs, get the leak rate and every deadline.
Try the free calculator

Written from the text of 40 CFR 84.102, 84.106 and 82.157 on eCFR (September 2026) and the EPA leak repair fact sheet (January 2026). Recordkeeping aid, not legal advice.

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