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Chemical Equation Balancer

In short: Balance any chemical equation instantly, including redox and ionic equations (MnO4- + Fe2+). It is free, works in your web browser and needs no download.

Type an unbalanced equation and get the smallest whole-number coefficients, with an atom-by-atom and charge check. Handles combustion, double displacement, redox and net ionic equations with charges.

Quick answer: enter reactants and products separated by = or ->, for example C3H8 + O2 = CO2 + H2O. The balancer returns C3H8 + 5 O2 → 3 CO2 + 4 H2O.
The balanced equation appears here.

Separate species with + (put spaces around + when you use ions). Write charges at the end: Fe3+, SO4^2- or SO42-, MnO4-. Coefficients you type are ignored and recalculated.

How to use the chemical equation balancer

  1. Type the reactants, an arrow (=, -> or →), then the products, for example Fe + O2 = Fe2O3.
  2. Check every formula is correct, because the balancer cannot fix a wrong product. Use capital letters for element symbols.
  3. Click Balance equation. You get the smallest whole-number coefficients and a table showing equal atoms (and charge) on both sides.
  4. Copy the result, or send it to the limiting reagent calculator or the net ionic equation calculator.

Worked examples

Propane combustion

C3H8 + O2 → CO2 + H2O

C3H8 + 5 O2 → 3 CO2 + 4 H2O

C: 3 = 3, H: 8 = 8, O: 10 = 6 + 4.

Copper with nitric acid (redox)

Cu + HNO3 → Cu(NO3)2 + NO + H2O

3 Cu + 8 HNO3 → 3 Cu(NO3)2 + 2 NO + 4 H2O

Permanganate oxidising iron(II)

MnO4− + Fe2+ + H+ → Mn2+ + Fe3+ + H2O

MnO4− + 5 Fe2+ + 8 H+ → Mn2+ + 5 Fe3+ + 4 H2O

Charge: +17 on both sides.

How the balancer works

Balancing means choosing coefficients so that every element, and the total charge, is the same on both sides (conservation of mass and charge). The tool writes one equation per element. For a + b → c + d, carbon gives a·Ca = c·Cc, and so on. It then solves the system exactly with fractions, the algebraic method, and scales the answer to the smallest whole numbers. This is the same result you get by inspection or by the half-reaction method, but it never misses a solution.

Σ (coefficient × atoms of element) on the left = Σ on the right, for every element and for charge

Balancing by hand (inspection method)

  1. Balance elements that appear in only one reactant and one product first (C, then H in combustion).
  2. Leave free elements such as O2, H2 or Fe until last.
  3. If you end with a fraction (e.g. 7/2 O2), multiply every coefficient by 2.
  4. Check atoms and charge once more.

When an equation cannot be balanced

If an element appears on only one side, or the only solution needs a negative coefficient, the reaction as written is impossible: a formula is wrong or a product is missing. Some equations are combinations of two independent reactions (for example H2 + O2 → H2O + H2O2). These have infinitely many balances, and the tool warns you and shows the smallest one.

Need a clean reaction scheme for a report? Draw structures, arrows and conditions in the free MolDraw reaction drawer.

Draw the reaction

Frequently asked questions

How do you balance a chemical equation?

Write the correct formulas, then change only the coefficients (never subscripts) until each element and the total charge are equal on both sides. This tool does it automatically with exact algebra.

Can this balance redox reactions?

Yes. Enter the full molecular equation (KMnO4 + HCl = KCl + MnCl2 + H2O + Cl2) or the ionic form with charges (MnO4- + Fe2+ + H+ = Mn2+ + Fe3+ + H2O); electrons are balanced through the charge equation.

How do I type charges and states?

Put the charge at the end of the formula: Na+, Fe3+, SO4^2- (or SO42-), MnO4-. State symbols such as (aq), (s), (g) and (l) are accepted and ignored for balancing.

Why does it say the equation cannot be balanced?

Usually a formula is wrong, a product is missing, or an element appears on only one side. Check the formulas and that reactants and products are on the correct sides.

Can coefficients be fractions?

Balanced equations are normally written with the smallest whole numbers. Fractions such as 7/2 O2 are sometimes used in thermochemistry, but this tool reports whole numbers.

What about the net ionic equation?

Use the net ionic equation calculator. It balances the equation, splits strong electrolytes into ions and cancels spectator ions.

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Need to sketch molecules for a report? Draw chemical structures online with MolDraw, a free online ChemDraw alternative (see the ChemDraw vs MolDraw comparison).

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