# Which method is used to calculate tonnes carbon from tonnes CO$_2$ equivalents of GHGs?

It appears that all GHGs are first translated into Carbon Dioxide Equivalents (CDEs) and that calculation is fairly straight forward.

Many report in tonnes of Carbon instead of tonnes CDE. I am unsure how this is calculated:

1. Actually count the carbon atoms in each species
2. Pretend that they really Carbon Dioxide, and simply apply 12/44 to tonnes of CDE to get a CDE carbon content. For example, nitric oxide has a CDE value but no actual carbon, but you can come up with a carbon mass using this approach.
3. Some other method

Is there a prescribed approach or standard basis?

• You convert to CO2-eq using global warming potential of the different GHGs and after you get the CO2-eq, you simply convert to C by the fraction 12/44. – y chung Feb 12 '20 at 17:36