Two greenhouse-gas metrics look nearly identical on the page but mean different things: CO₂ and CO₂e. The tool treats them as separate quantities with no conversion path between them, and this is one of its firmest rules.
What each one means
- CO₂ is carbon dioxide only — the mass of that one gas.
- CO₂e ("carbon dioxide equivalent") bundles multiple greenhouse gases — CO₂ plus methane (CH₄), nitrous oxide (N₂O) and others — each converted to a CO₂-equivalent mass using its global warming potential (GWP).
CO₂e is therefore not "more CO₂". It is a different metric that happens to be denominated in CO₂-equivalent units. There is no factor that turns one into the other in general, because the uplift depends entirely on the mix of other gases involved.
No conversion, ever
The tool keeps CO₂ and CO₂e as separate pseudo-dimensions with no path between them. If a source provides only CO₂, the result shows CO₂ and marks CO₂e "not available" — it never invents an uplift. It will refuse to convert a CO₂ figure to CO₂e or vice versa, explaining why. And because CO₂e depends on which GWP set was used (for example IPCC AR5 versus AR6, or 100-year versus 20-year horizons), comparing CO₂e figures from sources with different GWP sets is not apples-to-apples; the tool reports the source's stated GWP set where it is known.
Scope matters as much as the number
An emission figure is meaningless without its system boundary. The same fuel can be reported as direct combustion only, or as Scope 1 / 2 / 3, or well-to-tank, tank-to-wheel, or full well-to-wheel. Every emission result therefore states its metric, scope, energy basis, region and year together — a bare "kg CO₂" with none of that context is not something the tool will emit.
Two special cases
- Biogenic CO₂ (from wood, ethanol, biodiesel, biogas) is reported on its own labeled line, outside the main scopes — never silently zeroed inside a fossil total. The carbon really is emitted at the stack; the separate accounting reflects the biological carbon cycle, not zero physical emission.
- Hydrogen combustion produces
CO₂ = 0, a genuine physical fact (there is no carbon in H₂), shown with a "combustion only" label. But upstream emissions from producing that hydrogen are not zero — they depend on the production pathway and are context-required, never silently attached.
For grid electricity, the emission factor also depends on where and when the power was made; see why electricity emissions depend on region and year.