AFR Lambda Converter
Convert AFR and lambda across gasoline, E85, methanol, and race fuel scales.
Calculator guide
Converting AFR and lambda correctly
This converter expresses an AFR value as lambda, or a lambda value on the selected fuel’s AFR scale.
Inputs and calculation
- Fuel scale plus either the AFR or lambda value you want to convert.
Lambda = AFR ÷ stoichiometric AFR. AFR = lambda × stoichiometric AFR.
The selected reference values are 14.7 for gasoline and race gas, 9.8 for E85, and 6.4 for methanol.
How to interpret the result
- Lambda 1.00 is stoichiometric on any fuel scale; values below 1.00 are richer and values above 1.00 are leaner. Lambda is the clearest way to compare mixtures across fuels.
Assumptions and limits
- Real E85 ethanol content and race-fuel stoichiometry can differ from these reference values. Use the fuel supplier’s value when precision matters.
- This is a unit conversion, not a safe target recommendation; appropriate lambda depends on engine, load, fuel, and calibration strategy.
Example: one lambda, different AFR scales
Gasoline AFR 12.5 is about lambda 0.85. The same lambda on the 9.8 E85 scale is about 8.33 AFR.
Related guide
Connect fuel reference to log review
TuneWorks helps compare logged fuel data against the vehicle and session context.