Greenhouse Gas CO₂-Equivalent Calculator
Convert methane, nitrous oxide and F-gas emissions to CO₂-equivalent with IPCC AR6 global warming potentials over 100 or 20 years — totals, shares and the gas that dominates.
How it works
CO₂e = Σ mass_gas × GWP_gas; IPCC AR6 GWP-100: CH₄ 29.8 (fossil) / 27.2 (biogenic), N₂O 273, HFC-134a 1,526, SF₆ 25,200; GWP-20: CH₄ ≈ 81–83
Different gases trap different amounts of heat for different lengths of time. Global warming potential compares the warming from one kilogram of a gas with one kilogram of CO₂ over a chosen horizon: methane is intense but decays within about 12 years, so its GWP is ~30 over a century but ~80 over 20 years; nitrous oxide lasts a century and SF₆ millennia. National inventories use GWP-100 from the latest IPCC report (AR6); the 20-year view is argued for when near-term warming matters.
Worked example
1,000 kg CO₂ + 20 kg fossil methane + 1 kg N₂O: 1,000 + 596 + 273 = 1,869 kg CO₂e at GWP-100; at GWP-20 the methane alone becomes 1,650 kg and the total 2,923 kg.
Frequently asked questions
Why does biogenic methane have a lower GWP?
Its carbon was recently taken from the air, so the CO₂ it decays to is not counted as new; fossil methane adds fossil CO₂ as well.
Which horizon should I report?
GWP-100 is required by UNFCCC/GHG Protocol reporting; show GWP-20 alongside if methane is a big part of the footprint.
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This calculator is for educational purposes. Double-check important results before acting on them.