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ChemSolver

Chemical Equation Balancer

Balance chemical equations instantly and see coefficients, atom counts, and step-by-step results. This free equation balancer for chemistry runs entirely in your browser and shows exactly how each answer is computed.

How to Use the Chemical Equation Balancer

  1. Step 1

    Enter an unbalanced equation

    Type the reaction with an arrow: CH4 + O2 -> CO2 + H2O. Write the arrow as ->, =, or → — all three work. Formulas with parentheses such as Ca(OH)2 or Fe2(SO4)3 are fine, and existing coefficients are okay: the balancer will find the smallest whole-number set.

  2. Step 2

    Click Balance Equation

    The balancer counts every atom, sets up one conservation equation per element, and finds the smallest whole-number coefficients — the same answer a textbook would show. Everything runs in your browser; nothing is uploaded.

  3. Step 3

    Review the result

    Read the balanced equation with proper subscripts, the coefficient ratio, the atom-count check, the conservation verification, and the step-by-step explanation. Copy the equation for homework or lab notes, or clear the form and balance another.

How to Balance Chemical Equations

The balancer follows the same rules you use on paper. Here is the whole method — six habits that balance any equation cleanly.

  1. 1Write the correct formulas

    Balance an equation only after every reactant and product has its true formula. Copper(II) nitrate is Cu(NO3)2, not CuNO3 — a single wrong formula makes every later step pointless.

  2. 2Count atoms on both sides

    Tally each element on the reactant and product sides, including the atoms hidden inside parentheses: Fe2(SO4)3 holds 2 Fe, 3 S, and 12 O. The inventory tells you exactly which elements are out of balance and by how much.

  3. 3Change coefficients, never subscripts

    A coefficient multiplies the whole formula unit; a subscript would turn the substance into a different compound. 2H2O is two water molecules, but H2O2 is hydrogen peroxide. Balancing adjusts amounts, never identities.

  4. 4Balance one element at a time

    Start with an element that appears in the fewest formulas, and save free elements like O2, H2, or Cl2 for last — they sit in only one formula per side, so they are the easiest to fix. If a polyatomic ion such as SO4^2- or NO3- appears unchanged on both sides, balance it as a single unit instead of counting each element. In CH4 + O2 -> CO2 + H2O, balance carbon, then hydrogen, and let oxygen wait until the end.

  5. 5Reduce to the smallest whole-number ratio

    If a fraction shows up along the way — 7/2 O2 in an ethane combustion, say — finish the balance first, then multiply the whole equation to clear it. Finally divide out any common factor: 4H2 + 2O2 -> 4H2O is balanced, but the standard form is 2H2 + O2 -> 2H2O.

  6. 6Verify every element

    Recount all atoms at the end, parentheses included. In 4Fe + 3O2 -> 2Fe2O3, both sides hold 4 Fe and 6 O. If any element differs across the arrow, the equation is not balanced yet — the atom-count check in the tool above does this automatically for your equation.

The one rule students break most

Never change subscripts to balance an equation. Only coefficients may move — H2O2 is hydrogen peroxide, not "adjusted water."

Balancing Chemical Equations Examples

Each example shows the unbalanced equation, its balanced form, and the reason the coefficients land where they do — combustion, metal oxidation, neutralization, single displacement, and synthesis. Click an equation to load it into the balancer above, or open the equation page for the full write-up.

  • Hydrogen combustion

    H₂ + O₂ → H₂O2H₂ + O₂ → 2H₂O

    Diatomic O2 forces an even oxygen count. Doubling H2O makes 4 H on the right, so hydrogen doubles too.

    Equation details →

  • Methane combustion

    CH₄ + O₂ → CO₂ + H₂OCH₄ + 2O₂ → CO₂ + 2H₂O

    Carbon already matches 1:1. Hydrogen fixes H2O at 2, which leaves oxygen needing exactly 2 O2.

    Equation details →

  • Iron oxidation

    Fe + O₂ → Fe₂O₃4Fe + 3O₂ → 2Fe₂O₃

    Oxygen appears as O2 on the left and O3 per unit on the right — the least common multiple 6 gives 3 O2 and 2 Fe2O3, then iron follows with 4.

    Equation details →

  • HCl and NaOH neutralization

    HCl + NaOH → NaCl + H₂OHCl + NaOH → NaCl + H₂O

    Each side already holds 1 Na, 1 O, 1 Cl, and 2 H — a neutralization that arrives balanced at 1 : 1 : 1 : 1.

    Equation details →

  • Zinc and hydrochloric acid

    Zn + HCl → ZnCl₂ + H₂Zn + 2HCl → ZnCl₂ + H₂

    Zinc takes two chlorides, so HCl doubles; the leftover hydrogen pairs off as H2.

    Equation details →

  • Ammonia synthesis

    N₂ + H₂ → NH₃N₂ + 3H₂ → 2NH₃

    Three H per NH3 and diatomic H2 meet at the least common multiple 6: 2 NH3 and 3 H2, then nitrogen follows with 2.

    Equation details →

Popular Chemical Equations

The reactions that come up most often in chemistry courses and homework, each with its own page: balanced coefficients, atom counts, and reaction ratios.

What Is a Balanced Chemical Equation?

A balanced chemical equation has the same number of atoms of each element on the reactant and product sides. Atoms are neither created nor destroyed in a chemical reaction — they are only rearranged — so the totals on each side of the arrow must match exactly.

The coefficients in front of each formula give the ratio in which substances react and form. In 2H₂ + O₂ → 2H₂O, two hydrogen molecules react with one oxygen molecule to produce two water molecules: four H atoms and two O atoms on the left, four H and two O on the right. Those smallest whole-number coefficients are what this balancer computes, together with the atom-count check that proves conservation of mass for your reaction.

The substances to the left of the arrow are the reactants; those on the right are the products. Reading an equation becomes mechanical once you separate the two: identify the formulas, read the coefficients, and confirm that every element — reactants and products alike — appears in equal count on both sides.

Related Chemistry Calculators

Keep working the problem with the other free tools on this site. Once an equation is balanced, the coefficients become the mole ratios that drive every stoichiometry calculation.

Frequently Asked Questions

What is a chemical equation balancer?

A chemical equation balancer is a tool that finds the coefficients that make an equation obey conservation of mass: the same number of atoms of every element must appear on the reactant side and the product side. You type the unbalanced equation, and the balancer returns the smallest whole-number coefficients, an atom-by-atom check, and the reasoning behind the result.

How do I balance a chemical equation?

Write the correct formulas first, count the atoms of each element on both sides, then adjust coefficients — never subscripts — one element at a time until every count matches, and reduce the coefficients to the smallest whole-number ratio. Or skip the manual work: enter the equation above and the balancer shows the coefficients, the atom counts, and each step.

Can this calculator show the balancing steps?

Yes. Every result includes a step-by-step section — counting atoms, solving the conservation equations, and verifying the final counts — plus an algebraic method section that shows the exact equation system used to compute the coefficients. The steps are generated from the same calculation that produces the coefficients, so they always match the answer.

Can I enter an equation that already has coefficients?

Yes. If you enter something like 4H2 + 2O2 -> 4H2O, the balancer treats it as the reaction skeleton and recomputes the smallest whole-number coefficients — in this case 2H2 + O2 -> 2H2O. An already-balanced equation comes back unchanged, with a note confirming it.

Why can I change coefficients but not subscripts?

Coefficients change how many formula units take part in the reaction; subscripts change what the substance actually is. H2O and H2O2 are different compounds — water and hydrogen peroxide — so changing a subscript would describe a different reaction. Balancing only ever adjusts how many of each unchanged substance react and form.

How do I know if an equation is balanced?

Count the atoms of every element on both sides: the equation is balanced exactly when each element has the same count among the reactants and the products. The Atom Count Check table in the result does this automatically, with a ✓ for every element that matches.