FREE TOOL · STOICHIOMETRIC CONVERTER
Lambda ↔ AFR converter
Convert between Lambda (λ), Air-Fuel Ratio (AFR), and equivalence ratio (φ) for any common fuel. Tuners reading lambda from a wideband O2 sensor can instantly see the equivalent AFR for the fuel they're running.
What the numbers mean
| λ (Lambda) | AFR Gasoline | State | Typical use |
|---|---|---|---|
| 0.75-0.80 | 11.0-11.8 | Very rich | Peak power, knock margin |
| 0.85-0.90 | 12.5-13.2 | Rich | WOT power, turbo |
| 1.00 | 14.7 | Stoich | Idle, cruise, catalyst |
| 1.05-1.10 | 15.4-16.2 | Lean | Cruise economy |
| 1.15+ | 16.9+ | Very lean | EGT spike risk |
Modern petrol turbo OEM calibrations target λ 0.80-0.85 under WOT (rich) for knock protection and EGT control. Aggressive tunes often push λ down to 0.75 — at which point you start dumping fuel for no extra power and ruining the catalyst.