Chemical Equation Balancer

Exact coefficients, with every atom and every charge checked.

Balancing an equation means making the number of each kind of atom equal in the reactants and the products, as the law of conservation of mass requires (Lavoisier, 1789). This tool builds one row of a matrix per element, plus one row for electric charge when there are ions or electrons, and finds the set of coefficients that zeroes every row. The arithmetic uses exact fractions (no floating point), so the result is the smallest set of positive integers, with no rounding. For C3H8 + O2 → CO2 + H2O the system gives 3a = c, 8a = 2d and 2b = 2c + d, solved by a = 1, b = 5, c = 3 and d = 4. When an equation has more than one independent solution, the tool says so instead of inventing an answer (H2 + O2 → H2O + H2O2 mixes two reactions). When an element is missing on one side or a substance is on the wrong side, it says which. For redox, oxidation numbers come from the usual rules (groups 1 and 2, hydrogen +1, oxygen -2, halogens -1), the electrons transferred come from the total change in oxidation number and, in ionic form, the half-reactions are built by the ion-electron method in acidic or basic medium. Balancing does not prove the reaction happens: the tool checks the bookkeeping, not the chemistry.

Type the equation and read the result.

1. Type the equation with an arrow (->, → or =) and write charges with ^ (Fe^3+, SO4^2-), or pick a ready-made example. Coefficients you type are checked, not obeyed.
2. See the balanced equation, the atom table before and after, and the steps with the system of equations. Copy it as text, plain text or LaTeX (mhchem).
3. In the tabs, see the oxidation numbers, the oxidizing and reducing agents and the half-reactions, or enter masses in g or mol to find the limiting reagent and the yield.

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Sources and references for this tool

These references help contextualize formulas, standards, APIs and limitations used on this page. They do not replace professional validation when a result has legal, financial, medical or operational impact.

• Standard Atomic Weights 2024CIAAW / IUPAC, Standard atomic weights used in the stoichiometry.
• Abridged Standard Atomic Weights 2024CIAAW / IUPAC, Conventional values for elements whose weight is an interval.
• Avogadro constantNIST CODATA, Avogadro constant, exact since the 2019 SI.

Frequently asked questions

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