Combustion Reaction Calculator
Determine oxygen requirements and balanced equations for burning hydrocarbons and oxygen containing fuels to CO2 and H2O.
Balanced combustion reaction
2 C2H6 + 7 O2 -> 4 CO2 + 6 H2O
Moles of O2
7
Moles of CO2
4
Moles of H2O
6
How to Use This Calculator
Enter the fuel formula
Provide an elemental formula with C, H, and optional O. Examples include CH4, C8H18, or C6H10O2.
Balance with oxygen
The tool computes the stoichiometric oxygen demand so that products are CO2 and H2O.
Review integer coefficients
Fractional coefficients are automatically scaled to the smallest whole numbers.
Apply results to air calculations
Multiply the O2 requirement by 4.76 to estimate theoretical air demand (on a molar basis).
Formula
CxHyOz + (x + y/4 - z/2) O2 -> x CO2 + (y/2) H2O
Multiply coefficients as needed to obtain integers. Oxygenated fuels reduce the external O2 requirement by supplying oxygen internally.
Example
For C2H6: coefficients are 2 CO2, 3 H2O, and 3.5 O2. Multiplying by 2 yields 2 C2H6 + 7 O2 -> 4 CO2 + 6 H2O.
Full Description
Stoichiometric combustion requires enough oxygen to convert all carbon to carbon dioxide and hydrogen to water. Fuel oxygen offsets part of the oxygen demand.
This calculator balances the reaction automatically, making it easy to determine air requirements, emissions, or theoretical heat release for pure compounds.
Frequently Asked Questions
Does the calculator handle nitrogen or sulfur?
No. It focuses on C, H, and O compounds. Additional elements require separate balance considerations.
How do I include air instead of pure oxygen?
Multiply the O2 coefficient by 4.76 to estimate dry air moles (based on 21 percent O2).
Why are fractional coefficients allowed?
Fractional coefficients simplify balancing. The tool scales them to whole numbers automatically for reporting.
Can I balance alcohols or other oxygenates?
Yes. Enter formulas such as C2H5OH or C3H6O. The calculator accounts for the internal oxygen.
What if the oxygen requirement is negative?
Negative values indicate the fuel formula already contains more oxygen than needed. Recheck the input, as excess oxygen typically produces different products.