Chemistry
Combustion Reaction Calculator
Write the balanced combustion equation for any CxHyOz fuel and see how much oxygen it needs.
Your inputs
Change any value to update the result instantly.
Balanced combustion equation
C3H8 + 5O2 → 3CO2 + 4H2O
Oxygen needed per mole of fuel
5 mol
Carbon dioxide produced
3 mol
Water produced
4 mol
Oxygen for your amount of fuel
5 mol
Molar mass of the fuel
44.097 g/mol
This is complete combustion in plenty of oxygen. Fractional coefficients are doubled so every number is whole. Incomplete burning also gives carbon monoxide and soot.
What this calculator does
Writes the balanced complete-combustion equation for any CxHyOz fuel and the oxygen it needs.
What your result means
How much oxygen is consumed and how much carbon dioxide and water are produced per mole of fuel.
Formula and working
CxHyOz + (x + y/4 − z/2) O₂ → x CO₂ + (y/2) H₂O
- 1
Collect the inputs
Carbon atoms (x) = 3; Hydrogen atoms (y) = 8; Oxygen atoms (z) = 0; Fuel burned = 1 mol
- 2
Apply the formula
CxHyOz + (x + y/4 − z/2) O₂ → x CO₂ + (y/2) H₂O
- 3
Result
Balanced combustion equation = C3H8 + 5O2 → 3CO2 + 4H2O
Frequently asked questions
Symbols and assumptions
- x, y, z
- Carbon, hydrogen and oxygen atoms in the fuel
- ν
- Stoichiometric coefficient
- • Complete combustion in excess oxygen.
- • Fractional coefficients are doubled to whole numbers.
Sources and review
Reviewed 2026-09-22 · Next review 2027-09-22
- • Incomplete burning also produces carbon monoxide and soot, which this equation does not describe.
Important limitation
This is an educational estimate based only on the values and formula shown. Verify current rates, rules, units, and professional standards before relying on the result. It is not personalized financial or investment advice.
Report a mistake or request an improvement
Tell us if a formula, unit, explanation, or result needs attention. Your message will include this calculator’s name and page.
Related calculators
Combustion Analysis Calculator
Turn the carbon dioxide and water collected from burning a sample into its empirical and molecular formula.
Crude Protein Calculator
Convert a Kjeldahl nitrogen titration into the nitrogen and crude protein content of a sample.
Degree of Unsaturation Calculator
Count the rings and pi bonds hidden in a molecular formula before you draw the structure.
Double Bond Equivalent Calculator
Work out the DBE of a formula from mass spectrometry and split it into likely rings and double bonds.
Liquid Ethylene Density Calculator
Convert a measured mass and volume of liquid ethylene into density, with the reference saturated-liquid values alongside.
Actual Yield Calculator
Find the mass of product you should expect to collect from a known percent yield.