Science / Chemistry
Chemical Equation Balancer
Balance any chemical equation, including ionic and redox equations, with the smallest whole-number coefficients and an atom-by-atom check; mistakes in a formula are pointed out.
Chemical Equation Balancer: Each formula is read into counts of atoms, including brackets such as Ca(OH)2 and K4[Fe(CN)6], hydrates such as CuSO4·5H2O, and charges such as Fe^3+. Balancing means finding coefficients so that every element, and the total charge, is the same on both sides: a system of linear equations. The balancer solves it exactly with fractions, never rounding, then scales the answer to the smallest whole numbers. It works for equations with any number of substances. Runs 100% locally in your browser with zero server file uploads.
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C₃H₈ + 5O₂ → 3CO₂ + 4H₂O
| Element | Reactants | Products | |
|---|---|---|---|
| C | 3 | 3 | ✓ |
| H | 8 | 8 | ✓ |
| O | 10 | 10 | ✓ |
Write formulas with capital letters for elements, such as NaCl, Ca(OH)2, or CuSO4·5H2O. Write charges after ^, as in Fe^3+ or SO4^2-; a single + or - at the end, as in Na+ or Cl-, also works. Coefficients already written are ignored.
Balancing by hand
Start with the element that appears in the fewest formulas, and leave hydrogen and oxygen until last, since they often appear in water. Balance polyatomic ions such as SO4 as a unit when they pass through the reaction unchanged. If you end with a fraction, such as 7/2 O2, multiply every coefficient by the denominator.
For the arithmetic of moles and masses afterwards, use the scientific calculator.
Redox equations
In a redox reaction the electrons lost by one substance are gained by another. Writing the ions with their charges, such as MnO4^- and Fe^2+, and adding H^+ and H2O for an acidic solution, lets the balancer match both the atoms and the charge in one step, which gives the same answer as the half-equation method.
How to use it
- Type the equation with = or → between the two sides, such as Fe + O2 = Fe2O3.
- Read the balanced equation and the table that checks each element, and the charge for ions.
- If a formula is mistyped, the message shows where.
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Frequently asked questions
How do you balance a chemical equation?
Count the atoms of each element on both sides, then change the coefficients in front of the formulas, never the subscripts inside them, until every count matches. For Fe + O2 → Fe2O3, 4Fe + 3O2 → 2Fe2O3 has 4 iron and 6 oxygen atoms on each side.
How do I write ions and electrons?
Put the charge after ^: Fe^3+, SO4^2-, MnO4^-. A single + or - at the end also works for singly charged ions, as in Na+ and Cl-. Write an electron as e-. For ionic equations, the charge is balanced too.
Why does it say the equation cannot be balanced?
Usually a formula is wrong: a product that cannot form from the reactants, a missing substance, or a wrong charge. If an element appears on only one side, the message names it.
What does “more than one way” mean?
Some inputs, such as H2 + O2 → H2O + H2O2, are really two reactions added together, so any mix of them balances. Write each reaction separately to get a single answer.
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