The standardised way of measuring and comparing one's GHG emissions is to use the carbon dioxide equivalent (CO₂-eq), where other greenhouse gas effects are converted to CO₂ equivalencies. In this way, different activities/processes are measured and compared through CO₂ emissions.

For example, energy from natural gas emits less GHG than coal due to how it is produced. Coal produced in one country can also emit different GHG since the production process may differ.