Chemical equation balancer
Write the reactants and products with an arrow, for example C3H8 + O2 -> CO2 + H2O. The balancer finds the smallest whole-number coefficients, using exact fractions rather than trial and error.
Runs in your browser: nothing you enter is sent anywhere.
How to use it
- Type the reactants, an arrow, then the products. Capital letters start each element symbol.
- Read the balanced equation and the atom counts for each element underneath.
How it works
Each substance is a column and each element a row; the entry is how many atoms of that element the substance holds (negative for products). A balanced equation is a combination of columns that sums to zero, which is the null space of the matrix. The tool reduces the matrix with exact BigInt fractions, takes the one free direction, and clears denominators.
Worked example
C3H8 + O2 -> CO2 + H2O gives C3H8 + 5 O2 → 3 CO2 + 4 H2O: 3 C, 8 H and 10 O on each side. KMnO4 + HCl -> KCl + MnCl2 + Cl2 + H2O gives 2 KMnO4 + 16 HCl → 2 KCl + 2 MnCl2 + 5 Cl2 + 8 H2O.
Tips
- Spell each formula in full. CO is carbon monoxide, Co is cobalt.
- Leave out charges; use neutral compounds.
- Use the stoichiometry calculator next to turn the coefficients into grams.
Frequently asked questions
How does the balancer work?
It writes the number of atoms of each element in each substance as a matrix, with products counted negative, and solves it exactly with fractions (Gauss-Jordan elimination). The solution is scaled to the smallest whole numbers.
Why does it say more than one reaction fits?
When the substances allow two or more independent balanced reactions, for example H2 + O2 + H2O2 -> H2O, any mix of them also balances, so there is no single answer. Write them as separate equations.
Can it balance redox reactions with ions?
Not with charges. Write the full neutral formulas of the compounds instead, such as KMnO4 + HCl -> KCl + MnCl2 + Cl2 + H2O, which balances without charge bookkeeping.
Does the result check the chemistry?
It checks only that atoms are conserved. A balanced equation can still describe a reaction that does not happen, so the tool does not tell you whether the products are right.