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Methane to CO2e

1 tonne CH4 = 28 tonnes CO2e, using the global warming potential of 28 that 40 CFR 98 Table A-1 has required since 1 January 2025.

Multiply the mass of methane by its global warming potential. The argument is entirely about which potential, and the answer changed on 1 January 2025.

Factors last reviewed

Volume and energy

Volume to volume is fixed arithmetic. Volume to energy is not: it depends on how much heat your gas actually carries, so the heating value is a field you can edit.

BOE uses the SEC and industry convention of 6 Mcf to one barrel. That is an energy equivalence at the burner tip and says nothing about relative value at the wellhead, where the ratio is rarely 6:1.

The 1037 Btu/scf default is EIA's 2025 US average. EIA notes that heat content shifts with location, with the type of customer, and over time. If you have a gas analysis, type its number in instead.

scf
1,000
Mcf
1
MMcf
0.001
Bcf
0.000001
MMBtu
1.037
therm
10.37
GJ
1.0941
BOE
0.166667
Sm3
28.2623
Nm3
26.7911

Methane and nitrous oxide to CO2e

Mass times global warming potential. The potential you use depends on what you are filing under, and the two US answers differ by 12 percent, so pick the one that applies to you.

Effective 1 January 2025. What the EPA Greenhouse Gas Reporting Program requires today.

One standard atmosphere. The scientific and API base.

The list holds the two values US rules actually require. IPCC AR6 gives 29.8 for fossil methane, 27.0 for non-fossil, and 273 for nitrous oxide (IPCC AR6 Working Group I, Table 7.15). Fossil is the one covering oil and gas leaks. Why it is not in this list.

Gas mass
1
tonnes
CO2e
28
tonnes CO2e
CO2e
28,000
kg CO2e
Multiplier used
28
GWP, 100-year

Volume inputs assume pure gas at 60 °F and the pressure base you picked, against a molar mass of 16.043 for methane. The base matters: Texas reports at 14.65 psia, so running RRC volumes through the 14.696 default overstates mass, and CO 2e with it, by about 0.31 percent. Real pipeline gas is also a mixture, so a measured mass will beat this for anything you have to defend.

Emission rate

A leak survey reports grams or kilograms an hour. A permit is written in tonnes a year. An engineer thinks in scfh. Same leak, three vocabularies.

Annualised at 8,760 hours, and volume rates cross to mass through the same standard-condition density the CO2e panel uses, so a leak quoted in scfh and the same leak in kg/hr cannot disagree.

kg/hr
1
g/hr
1,000
kg/day
24
t/yr
8.76
scfh
52.148
Mcf/d
1.2516

Methane to CO2e formula

CO2e = mass of methane x global warming potential

The factor is the part worth checking. It is a field in the calculator above, and its source is named on the full converter.

Methane to CO2e chart

Tonnes CH4 t CO2e (GWP 28) t CO2e (AR4 25)
0.1 2.8 2.5
0.5 14 12.5
1 28 25
5 140 125
10 280 250
25 700 625
50 1,400 1,250
100 2,800 2,500
500 14,000 12,500
1,000 28,000 25,000

Frequently asked questions

What is the CO2e of 1 tonne of methane?

Multiply by 28, the potential 40 CFR 98 Table A-1 has required since 1 January 2025, which puts one tonne at 28 tonnes CO2e. Inverted, one tonne of CO2e corresponds to 0.035714 tonnes of methane. Starting from a volume instead, one Mcf of pure methane comes to 536.93 kg CO2e at standard conditions.

Should I use 25 or 28 for methane?

For anything filed under 40 CFR 98, use 28: that is what Table A-1 has required since 1 January 2025, after the final rule published on 25 April 2024. Use 25 only if the programme you are reporting to still specifies the older AR4 value, which several state programmes do. A lot of published guidance, including EPA pages, has not caught up, so check the rule rather than a summary of it.

How do I convert a volume of methane to CO2e?

Convert the volume to a mass first, which needs standard conditions and a pressure base, then apply the potential. The full converter does both steps and lets you pick the base, which matters because Texas reports gas at 14.65 psia rather than 14.696.

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