Chemical Equation Balancer
Enter an unbalanced equation (like Fe + O2 -> Fe2O3) using + between compounds and -> between reactants and products.
Last updated: September 26, 2026
Frequently asked questions
What does it mean to 'balance' a chemical equation?
Finding the whole-number coefficients (multipliers) in front of each compound so the same number of atoms of each element appears on both sides of the equation - matter isn't created or destroyed in a chemical reaction, so both sides must balance exactly.
How do I enter an equation with multiple compounds, like combustion reactions?
Separate compounds with + and use -> between reactants and products, for example: CH4 + O2 -> CO2 + H2O. This calculator finds the smallest whole-number coefficients that balance every element in the equation.
Why does this calculator sometimes say it can't balance my equation?
Usually because of a typo in a chemical formula, or because the reaction as written isn't chemically valid (the same elements don't appear on both sides). Double-check each formula's capitalization and parentheses - chemical symbols are case-sensitive (Co is cobalt, CO is carbon monoxide).
Why do balanced coefficients need to be the smallest possible whole numbers?
Any multiple of a balanced set of coefficients (like doubling every coefficient) is technically still balanced, but chemists use the smallest whole-number ratio by convention since it represents the simplest, most standard way to express the reaction.
Can this balance equations that include ionic charges, like Fe³⁺ + e⁻ → Fe?
This calculator is built for balancing atoms in molecular equations, not charge-balancing half-reactions - redox half-reactions with electrons and ionic charges need a separate charge-balancing step in addition to atom balancing.
What's the balanced equation for the combustion of methane (CH4 + O2 -> CO2 + H2O)?
CH₄ + 2O₂ → CO₂ + 2H₂O - one methane molecule needs two oxygen molecules to fully convert its carbon to CO₂ and its four hydrogens to two water molecules, balancing 1 C, 4 H, and 4 O on each side.
Can this balance the combustion of any hydrocarbon, like propane or octane?
Yes. Enter the hydrocarbon plus O2 on the left and CO2 + H2O on the right, for example C3H8 + O2 -> CO2 + H2O or C8H18 + O2 -> CO2 + H2O, and the calculator finds the whole-number coefficients for complete combustion. This is a symbolic, idealized combustion equation - it doesn't cover incomplete combustion, real fuel-air ratios, or how to carry out a combustion reaction.