Air/Fuel Ratio Calculator
Convert between AFR and Lambda for different fuels.
Target AFR Reference (Gasoline)
| Condition | AFR | Lambda |
|---|---|---|
| Stoichiometric | 14.7:1 | 1.00 |
| Best Power (WOT) | 12.5-13.0:1 | 0.85-0.88 |
| Best Economy | 15.5-16.5:1 | 1.05-1.12 |
| Safe Boost (turbo) | 11.5-12.0:1 | 0.78-0.82 |
| Idle | 14.0-15.0:1 | 0.95-1.02 |
| Cruise | 14.7-15.5:1 | 1.00-1.05 |
Understanding AFR and Lambda
Air/Fuel Ratio (AFR)
The mass ratio of air to fuel in the combustion mixture. For gasoline, 14.7:1 means 14.7 parts air to 1 part fuel by mass.
Lambda
Lambda = AFR / Stoichiometric AFR. Lambda 1.0 = stoichiometric, <1.0 = rich, >1.0 = lean. Lambda is fuel-independent.