How do I calculate the GWP of a refrigerant blend like R-404A, R-407C or R-410A?

Multiply each component's mass fraction by its GWP and add the results. R-404A is 44% R-125, 52% R-143a and 4% R-134a, so its AR6 GWP is 0.44 x 3,740 + 0.52 x 5,810 + 0.04 x 1,530 = 4,728. Use one IPCC report, AR5 or AR6, for every gas.

Compositions of common blends

Use the nominal composition by mass from ASHRAE Standard 34 or the gas maker's safety data sheet. Fractions must add to 100 percent.

• R-410A: R-32 50%, R-125 50%.
• R-407C: R-32 23%, R-125 25%, R-134a 52%.
• R-404A: R-125 44%, R-143a 52%, R-134a 4%.

Component GWPs (100-year)

AR5 values are from Working Group I Chapter 8, Table 8.A.1; AR6 values from Chapter 7, Table 7.SM.7.

• R-32 (HFC-32): 677 in AR5, 771 in AR6.
• R-125 (HFC-125): 3,170 in AR5, 3,740 in AR6.
• R-134a (HFC-134a): 1,300 in AR5, 1,530 in AR6.
• R-143a (HFC-143a): 4,800 in AR5, 5,810 in AR6.

Results for the three blends

• R-410A: AR5 0.5 x 677 + 0.5 x 3,170 = 1,923.5. AR6 2,255.5.
• R-407C: AR5 0.23 x 677 + 0.25 x 3,170 + 0.52 x 1,300 = 155.7 + 792.5 + 676 = 1,624.2. AR6 0.23 x 771 + 0.25 x 3,740 + 0.52 x 1,530 = 177.3 + 935 + 795.6 = 1,907.9.
• R-404A: AR5 0.44 x 3,170 + 0.52 x 4,800 + 0.04 x 1,300 = 1,394.8 + 2,496 + 52 = 3,942.8. AR6 0.44 x 3,740 + 0.52 x 5,810 + 0.04 x 1,530 = 1,645.6 + 3,021.2 + 61.2 = 4,728.0.

Mistakes to avoid

• Using mole fractions instead of mass fractions. Blend names give mass shares.
• Mixing sets, such as AR4 values from an old label with AR6 values for other gases. Older AR4 based figures, such as 2,088 for R-410A, appear on many labels and quotes.
• Treating a blend that contains R-22 or another HCFC as fully Scope 1. Split it: the HFC share goes in Scope 1 and the HCFC share is reported separately, outside the scope totals.
• Taking a GWP printed on an invoice without checking which IPCC report it comes from.

Worked example: one year of top-ups at a cold store

• Top-ups: 20 kg of R-404A and 8 kg of R-407C
• AR6: 20 x 4,728.0 + 8 x 1,907.9 = 94,560 + 15,263 = 109,823 kg CO2e, about 109.8 t
• AR5: 20 x 3,942.8 + 8 x 1,624.2 = 78,856 + 12,994 = 91,850 kg CO2e, about 91.8 t
• The AR6 total is about 20 percent higher for the same gas, so name the report you used

What Senseible does here

Senseible keeps refrigerant service and purchase invoices as evidence and calculates refrigerant CO2e when you give the gas and the kilograms charged into equipment; a gas purchase alone is not counted as leakage. The AR5 or AR6 choice changes only these gas figures, not its fuel and grid CO2 factors.

• Refrigerant top-up invoice to CO2e
• AR5 or AR6 GWP: which to use
• Does R-22 count in Scope 1?
• HSN codes for refrigerant gases

Sources: IPCC AR6 WG1, Chapter 7 Supplementary Material, Table 7.SM.7 (GWP100), IPCC AR5 WG1, Chapter 8, Appendix 8.A, Table 8.A.1 (GWP100), GHG Protocol Corporate Standard (HFCs in Scope 1; HCFCs reported separately)

Last reviewed 2026-10-18.