How to use it
- Type the reactants, an arrow and the products, for example C3H8 + O2 -> CO2 + H2O. Separate the species with a plus sign and spaces.
- For ions, write the charge after the formula, for example MnO4- + Fe2+ + H+ -> Mn2+ + Fe3+ + H2O.
- Read the Balanced equation and the Coefficients table. The Check table shows that each element and the charge match on both sides.
- If the page says an element is on one side only, or that the answer is not single, check the species. The message gives the reason.
How the coefficients are found
Each element gives one equation: the atoms of that element on the left, counted with their coefficients, equal the atoms on the right. When ions are present, the total charge gives one more equation. The coefficients are the unknowns of this linear system.
The system is solved with exact fractions by Gauss-Jordan elimination, so no rounding enters. The answer is then scaled to the smallest whole numbers, which is how a balanced equation is usually written.
For each element e: Σ(reactants) nₑ,ᵢ × xᵢ − Σ(products) nₑ,ⱼ × xⱼ = 0When there is no single answer
- One free direction: there is exactly one set of smallest whole numbers, and the working shows it.
- Two or more free directions: the atoms do not fix the coefficients. C + O2 -> CO + CO2 is an example: both 2 C + O2 -> 2 CO and C + O2 -> CO2 balance it.
- No positive solution: a balancing would need a negative amount of a species. H2O2 -> H2O + H2 is an example.
- An element on one side only: no balancing is possible, because nothing on the other side can supply or use that element.
What this tool does not do
It balances atoms and charge. It does not predict the products of a reaction, and it does not add electrons to a half-reaction. Type the reaction you mean, with the products written in full.
Worked example: propane burning in oxygen
Propane (C3H8) burns in oxygen to give carbon dioxide and water. Let a, b, c and d be the coefficients of C3H8, O2, CO2 and H2O. Carbon gives 3a = c, hydrogen gives 8a = 2d and oxygen gives 2b = 2c + d.
The tool sets the free letter d to 1, which gives a = 1/4, b = 5/4 and c = 3/4. Multiplying all of them by 4 gives 1, 5, 3 and 4: C3H8 + 5 O2 → 3 CO2 + 4 H2O.
| Species | Coefficient |
|---|---|
| C3H8 | 1 |
| O2 | 5 |
| CO2 | 3 |
| H2O | 4 |
Frequently asked questions
What does it mean to balance an equation?
It means the same number of atoms of each element, and the same total charge, are on both sides. Balancing puts whole-number coefficients in front of the species, and it never changes a formula.
Why are the coefficients the smallest whole numbers?
Chemists write the smallest whole numbers because they give the simplest ratio of amounts. Multiplying every coefficient by the same number, such as 2, also balances the equation, but it is not the usual form.
Why does the tool say that the equation has many answers?
When two independent ways of balancing exist, as in C + O2 -> CO + CO2, the atoms cannot choose one set of coefficients. Check that every reactant and product is written in full, because a missing species often causes this.
Can it balance an equation with electrons or in an acid solution?
Not with electrons as species. The tool balances atoms and charge, so an ionic equation such as MnO4- + Fe2+ + H+ -> Mn2+ + Fe3+ + H2O works, but a half-reaction with electrons does not.
Does the tool show the products of a reaction?
No. You type the reactants and the products. The tool balances them, and it reports when no balancing exists, which can point to a wrong formula or a missing product.
Does the calculator keep my equation or send it anywhere?
No. The balancing runs in your browser, and nothing you type is stored or sent to our server.
Sources
Figures and text last checked on Tuesday, November 10, 2026.