Stoichiometric Air Requirement Calculator
The Exact Air a Fuel Needs to Burn Completely
Stoichiometric air requirement is the theoretical minimum air needed to burn a fuel completely, with nothing left over on either side of the reaction. It's calculated directly from a fuel's ultimate analysis — the percentage of carbon, hydrogen, oxygen, and sulfur by mass.
The Formula
Theoretical Air = 11.5C + 34.5(H − O/8) + 4.32S
C, H, O, and S are mass fractions from the fuel's ultimate analysis (as decimals), and the result is in kg of air per kg of fuel.
Worked Example
For a fuel that is 84% carbon, 12% hydrogen, 2% oxygen, and 1% sulfur:
Air = 11.5(0.84) + 34.5(0.12 − 0.02/8) + 4.32(0.01) = 13.63 kg air/kg fuel
How to Use This Calculator
- Enter the fuel's Carbon and Hydrogen percentage by mass.
- Enter Oxygen and Sulfur percentage if known (optional, defaults to 0).
- Select Calculate to get the theoretical air requirement.
Related Calculations
Add a safety margin with the Excess Air Calculator, or find actual air supply needed in the Actual Air Requirement Calculator.