Type an unbalanced reaction and this free chemical equation balancer finds the smallest whole-number coefficients, then proves it with an atom-by-atom (and charge) check. It handles combustion, precipitation, ionic and redox equations, and lists each substance’s molar mass for stoichiometry.
How the balancer works
Balancing means every element (and the total charge) is the same on both sides. The calculator writes one equation per element, for example for C₃H₈ + O₂ → CO₂ + H₂O with coefficients a, b, c, d:
It solves this system exactly with fractions (Gaussian elimination to find the null space of the composition matrix), then scales to the smallest whole numbers. This algebraic method works where trial and error gets slow, such as redox reactions with six or more substances.
Tips for balancing by hand
- Balance elements that appear in only one substance on each side first.
- Treat polyatomic ions such as SO₄²⁻ as a single unit if they stay intact.
- Leave hydrogen and oxygen until last, and free elements (O₂, Fe) to the very end.
- Never change subscripts, only coefficients. Changing H₂O to H₂O₂ makes a different substance.
Frequently asked questions
How do I balance a chemical equation?
Type the reactants and products separated by = or ->, with + between substances, e.g. Fe + O2 = Fe2O3, and press Balance. The calculator gives 4Fe + 3O2 → 2Fe2O3 and checks every element.
Can it balance redox and ionic equations?
Yes. Write charges with a caret, such as MnO4^- or Fe^3+, and include H^+, OH^- or H2O if the reaction needs them. The calculator balances charge as well as atoms.
Why does it say the equation cannot be balanced?
Either a substance is wrong (check capital letters and subscripts), a reactant or product is missing, or an element appears on only one side. Also make sure you used real formulas, since subscripts can’t change.
What if there is more than one way to balance it?
Some equations combine two independent reactions, so many coefficient sets work. The calculator tells you when this happens; splitting it into separate reactions gives a unique answer.
Do I need to enter state symbols?
No. Labels like (s), (l), (g) and (aq) are accepted and ignored for balancing.
Related tools
Free educational tool by HawkInc. Results are calculated in your browser and rounded for display; check critical work by hand or with a second method.