Chemical Equation Balancer

Type the reactants and products. The balancer finds the smallest whole-number coefficients and proves the result with an atom count and a mass check.

Separate substances with +, sides with -> or =. Coefficients are optional; the equation is balanced for you.

C₃H₈ + 5O₂ → 3CO₂ + 4H₂O

Atom count on each side
ElementReactant sideProduct sideBalanced?
C33✓ yes
H88✓ yes
O1010✓ yes
Σr
Mass of reactants (per mole of reaction)
204.087g
Σp
Mass of products
204.087g
Equal masses: conservation of mass holds

Next: use this equation in the stoichiometry calculator or find the limiting reactant.

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Balancing by the matrix method: a worked example

Take propane burning: a C₃H₈ + b O₂ → c CO₂ + d H₂O. Each element gives one equation:

  • Carbon: 3a = c
  • Hydrogen: 8a = 2d
  • Oxygen: 2b = 2c + d

Set a = 1. Then c = 3, d = 4 and 2b = 6 + 4, so b = 5. The balanced equation is C₃H₈ + 5O₂ → 3CO₂ + 4H₂O. With four unknowns and three equations there is exactly one free choice, which is why the ratio is fixed but the scale is not: 2, 10, 6, 8 is also balanced, just not in lowest terms.

Why balancing matters

Atoms are neither created nor destroyed in a chemical reaction (Lavoisier’s law of conservation of mass). The coefficients are the mole ratios you use in every stoichiometry calculation, so a wrong coefficient makes every later number wrong.

Frequently asked questions

How does the equation balancer work?
It writes one equation per element saying “atoms in = atoms out”, then solves that system exactly with fractions (Gaussian elimination) and scales the answer to the smallest whole numbers. That is the matrix method taught in linear algebra, so it handles redox equations that are painful by inspection.
Why does it say the equation has more than one way to balance?
Some “equations” are really two reactions added together, e.g. H₂O₂ → H₂O + O₂ + H₂. The atom-balance system then has infinitely many independent solutions. Split it into separate reactions and balance each one.
Can I balance ionic equations with charges?
Not yet in the charge sense: the balancer counts atoms only. For half-equations, balance atoms here, then add electrons to equalise charge by hand.
Do I have to type the state symbols?
No. (aq), (s), (l) and (g) at the end of a formula are ignored, as are any coefficients you typed.
How do I balance an equation by inspection?
Start with the most complicated molecule, balance elements that appear in only one substance on each side first, leave free elements (O₂, H₂, Fe) until last, and clear fractions at the end by multiplying through.