Air to Fuel Ratio Calculator: The Global Standard for Combustion Tuning
Used by engine tuners, emissions engineers, and OEMs worldwide, our air to fuel ratio calculator optimizes performance across gasoline, diesel, and alternative fuels.
"Aequilibrium perfectum" — Perfect balance.
How the Air to Fuel Ratio Calculator Works
Core equations:
AFR = m_air / m_fuel
λ = AFR_actual / AFR_stoich
Fuel Flow = Power × BSFC / 3600
λ = AFR_actual / AFR_stoich
Fuel Flow = Power × BSFC / 3600
Air to Fuel Ratio Calculator: Four Powerful Modes
Mass Ratio Mode
Direct AFR calculation in our air to fuel ratio calculator.
Volume Ratio Mode
Convert mass to volume using density.
Lambda Mode
Real-time lambda from AFR or O2 sensor.
Fuel Injection Mode
Injector sizing and duty cycle.
Air to Fuel Ratio Calculator: Stoichiometric Values
| Fuel | AFR Stoich | Lambda = 1 |
|---|---|---|
| Gasoline | 14.7:1 | 1.00 |
| Diesel | 14.5:1 | 1.00 |
| Methanol | 6.4:1 | 1.00 |
Air to Fuel Ratio Calculator: Operating Ranges
- Rich: AFR < 14.0 (λ < 0.95) — Max power
- Stoichiometric: AFR = 14.7 (λ = 1.00) — Emissions
- Lean: AFR > 15.0 (λ > 1.02) — Economy
- Cruise: 15.5–16.5:1
- Idle: 13.5–14.5:1
Pro Tips for the Air to Fuel Ratio Calculator
- Target λ = 0.85 for WOT
- Use wideband O2 for accuracy
- Correct for altitude: -1% AFR per 300m
- Ethanol blend: +4% fuel flow
- Log AFR vs RPM for tuning
Tune for Perfection
From dyno to drag strip, our air to fuel ratio calculator delivers championship results.
Calculate AFR