Chemical equation balancer
Type a reaction and get the smallest whole-number coefficients, with every element (and charge) counted on both sides so you can check it yourself.
How to balance a chemical equation
A balanced equation has the same number of each kind of atom on both sides, because atoms aren’t created or destroyed in a reaction. You change only the coefficients in front of each formula, never the subscripts.
- Write the correct formula for every reactant and product.
- Balance elements that appear in only one compound on each side first, and leave hydrogen and oxygen for last.
- Adjust coefficients until every element matches, then reduce to the smallest whole numbers.
Example, propane combustion: C₃H₈ + 5O₂ → 3CO₂ + 4H₂O. Carbon 3 = 3, hydrogen 8 = 8, oxygen 10 = 6 + 4.
How this balancer works
It uses the algebraic method: one equation per element, with an unknown coefficient for each species. Solving that system with exact fractions gives the unique smallest set of whole numbers, so it handles equations that are hard to balance by trial and error.
If an element appears on only one side, or a reaction could balance more than one way (often two reactions written as one), it tells you instead of guessing.
Ionic and redox equations
Add charges with a caret, like Fe^3+ or SO4^2-, and write electrons as e-. Charge is balanced along with the atoms.
Example: MnO₄⁻ + 5Fe²⁺ + 8H⁺ → Mn²⁺ + 5Fe³⁺ + 4H₂O. The total charge is +17 on both sides.
After you balance
Balanced coefficients give the mole ratios for stoichiometry. In 4Fe + 3O₂ → 2Fe₂O₃, 4 mol of iron makes 2 mol of iron(III) oxide. Use the molar mass calculator to convert those moles to grams.
Common questions.
Why can’t I change the subscripts to balance an equation?
Subscripts define the substance. Changing H₂O to H₂O₂ turns water into hydrogen peroxide. Only coefficients, the numbers in front, can change.
What does “cannot be balanced” mean?
Usually a formula is wrong, or a product is missing. Every element on the left must also appear on the right. Check the formulas and charges.
Can it balance redox reactions in acidic or basic solution?
Yes, if you include H⁺ and H₂O (acidic) or OH⁻ and H₂O (basic) as species, it balances atoms and charge together. For the half-reaction method step by step, ask the AI solver.
Does it work with fractions or decimals?
It always returns the smallest whole-number coefficients. If your class uses fractional coefficients for one mole of a product, divide the result by the coefficient you want to be 1.