Chemical Equation Balancer
Type an equation such as Fe + O2 → Fe2O3 and get the smallest whole-number coefficients at once — with a count of every atom on both sides, molar masses, and the grams and moles that react.
At a glance
- Balances chemical equations with the smallest whole-number coefficients, worked out exactly — never by trial and error or rounding.
- Handles brackets (
Ca3(PO4)2), hydrates (CuSO4.5H2O), complex ions ([Fe(CN)6]^4-), states of matter and reversible arrows. - Balances ionic equations and half-reactions by charge as well as atoms:
MnO4- + Fe2+ + H+ → Mn2+ + Fe3+ + H2Obecomes 1, 5, 8 → 1, 5, 4. - Shows a check table — atoms of each element, total charge and mass on both sides — so you can see the equation is balanced.
- Gives the molar mass of every substance from IUPAC standard atomic weights, and works out the grams and moles of everything from one amount you enter.
- Finds the limiting reactant and how much of the others is left over when you enter amounts for two or more reactants.
- Names the reaction type where the pattern settles it: synthesis, decomposition, combustion, single or double displacement, neutralisation.
- When an equation cannot be balanced, it says why: an element on one side only, a substance on the wrong side, or charges that cannot match.
Step by step
How to balance a chemical equation
- 1
Type the equation
Write the reactants, an arrow and the products, with + between substances:
C3H8 + O2 -> CO2 + H2O. Leave the coefficients out. - 2
Use capitals and digits
Element symbols need their capital letters (
Cois cobalt,COis carbon monoxide). Type subscripts as plain digits and charges after^:Fe^3+. - 3
Read the result
The balanced equation appears as you type, with the reaction type and a table that counts each element on both sides.
- 4
Work out amounts
In the amounts table, type the grams or moles of one substance to see how much of each other substance reacts or forms.
Features
Everything you need, nothing you don’t
Exact, every time
The coefficients come from solving the element and charge equations in fractions, so even long redox equations with coefficients in the hundreds are right.
Type it the way you write it
H2SO4, Fe^3+, SO4^2-, e-, CuSO4.5H2O — or paste H₂SO₄ and Fe³⁺ straight from a document. Any arrow works: ->, =, → or ⇌.
Proof on the page
Every element is counted on the left and the right, with the charge and the mass, so you can show your working.
Stoichiometry built in
Enter grams or moles of one substance to get all the others; enter two reactants to find the limiting one and the excess.
Helpful when it fails
A wrong capital letter, a missing product or an unbalanced charge gets a plain explanation instead of “error”.
Private and free
Everything is calculated in your browser. No sign-up, no limits.
How to type formulas
| To write | Type | Example |
|---|---|---|
| A subscript | the digit after the symbol | H2O, C6H12O6 |
| A group in brackets | ( ) or [ ] with a digit after | Ca(OH)2, Al2(SO4)3, K4[Fe(CN)6] |
| Water of crystallisation | a dot or * | CuSO4.5H2O |
| A charge | ^ then the charge | Fe^3+, SO4^2-, NH4^+ |
| An electron | e- | Fe^3+ + e- -> Fe^2+ |
| A state | (s), (l), (g) or (aq) after the formula | NaCl(aq) |
| The arrow | -> or = (⇌ or <-> for reversible) | N2 + H2 <-> NH3 |
Worked examples
| You type | Balanced |
|---|---|
H2 + O2 -> H2O | 2 H₂ + O₂ → 2 H₂O |
Fe + O2 -> Fe2O3 | 4 Fe + 3 O₂ → 2 Fe₂O₃ |
C3H8 + O2 -> CO2 + H2O | C₃H₈ + 5 O₂ → 3 CO₂ + 4 H₂O |
Al + H2SO4 -> Al2(SO4)3 + H2 | 2 Al + 3 H₂SO₄ → Al₂(SO₄)₃ + 3 H₂ |
KMnO4 + HCl -> KCl + MnCl2 + H2O + Cl2 | 2 KMnO₄ + 16 HCl → 2 KCl + 2 MnCl₂ + 8 H₂O + 5 Cl₂ |
Cr2O7^2- + H+ + e- -> Cr^3+ + H2O | Cr₂O₇²⁻ + 14 H⁺ + 6 e⁻ → 2 Cr³⁺ + 7 H₂O |
How the balancing works
A balanced equation has the same number of atoms of every element on both sides, and the same total charge. Each element gives one equation in the unknown coefficients: for hydrogen in H₂ + O₂ → H₂O, twice the coefficient of H₂ must equal twice the coefficient of H₂O.
The tool solves all of those equations together, exactly, and scales the answer to the smallest whole numbers. If there is no solution, the equation cannot be balanced as written — usually a formula is wrong or a substance is missing. If there is more than one independent solution, the equation is really two reactions written as one (for example C + O₂ → CO + CO₂), and the tool tells you so.
Digits before a + or − sign
Plain text cannot tell a charge from a subscript: Fe3+ should be Fe³⁺ but I3- is I₃⁻. The tool reads a digit before the sign as the charge on a single atom (Fe3+, Cu2+, O2-) and as a subscript in anything larger (MnO4-, NH4+); two digits are split (SO42- is SO₄²⁻). If that reading cannot be balanced it tries the other, and it always shows how each ion was read. Write Fe^3+ or I3^- to leave no doubt.
FAQ
Frequently asked questions
Why does it say an element appears on only one side?
CL for Cl or NA for Na.Can it balance redox equations?
KMnO4 + HCl -> KCl + MnCl2 + H2O + Cl2 are balanced directly. For ionic ones, include the H⁺ or OH⁻ and H₂O that take part, for example MnO4- + Fe2+ + H+ -> Mn2+ + Fe3+ + H2O; charges are balanced along with the atoms. Half-reactions with e- work too.What does “more than one balanced form” mean?
C + O2 -> CO + CO2. They have endless valid sets of coefficients. The tool shows one small set and says so; split the equation into its separate reactions for a definite answer.How is the limiting reactant found?
Which atomic weights are used?
Do I need to type the coefficients?
Does it show the steps?
Keep going
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