Calculate air-fuel ratio from air and fuel mass, or find lambda and equivalence ratio from actual and stoichiometric AFR with fuel presets.

AFR & Lambda (Air/Fuel Ratio) Calculator

Enter any 2 values to calculate the missing variable.

Tip: AFR = (mass of air) ÷ (mass of fuel)

Related Calculators

Lambda Air/Fuel Ratio Formula

The following formula is used to calculate the lambda air/fuel ratio for a given actual and stoichiometric air/fuel ratio.

λ = (AFR₍actual)) / (AFR₍stoich))

Variables:

  • λ is the lambda value
  • AFRactual is the actual air/fuel ratio
  • AFRstoich is the stoichiometric air/fuel ratio

To calculate the lambda value, divide the actual air/fuel ratio by the stoichiometric air/fuel ratio.

What is a Lambda Air/Fuel Ratio?

The lambda air/fuel ratio is a measure of the air-to-fuel mixture in an internal combustion engine. It is used to determine whether the engine is running lean (too much air) or rich (too much fuel). A lambda value of 1 indicates a stoichiometric mixture, where the air and fuel are in perfect balance for complete combustion. Values less than 1 indicate a rich mixture, while values greater than 1 indicate a lean mixture. Monitoring and adjusting the lambda value is crucial for optimizing engine performance, fuel efficiency, and emissions.

How to Calculate Lambda Air/Fuel Ratio?

The following steps outline how to calculate the Lambda Air/Fuel Ratio.

  1. First, determine the actual air/fuel ratio (AFRactual).
  2. Next, determine the stoichiometric air/fuel ratio (AFRstoich).
  3. Finally, calculate the lambda value using the formula λ = AFRactual / AFRstoich.
  4. After inserting the values and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

Actual Air/Fuel Ratio (AFRactual) = 14.7

Stoichiometric Air/Fuel Ratio (AFRstoich) = 14.7