Chemical Equation Balancer
Enter an unbalanced chemical equation and get it balanced instantly. Supports any number of reactants and products, parentheses, brackets, hydrates, and polyatomic ions.
How to Balance Chemical Equations
Balancing a chemical equation by hand follows these five steps:
- Write the unbalanced equation with all reactants on the left and all products on the right.
- List every element present and count atoms of each on both sides.
- Start with the most complex compound — the one with the most atoms or the most different elements. This usually constrains the other coefficients.
- Adjust coefficients (the numbers before formulas) until every element has equal atom counts. Never change subscripts.
- Verify by counting atoms of each element on both sides one final time.
Example — Fe + O₂ → Fe₂O₃: The most complex is Fe₂O₃. Put a 2 in front of it to get even oxygen (6 atoms). Balance O on the left with 3O₂ (6 atoms). That forces 4Fe on the left. Final: 4Fe + 3O₂ → 2Fe₂O₃.
What is a Balanced Chemical Equation?
A chemical equation is balanced when it obeys the law of conservation of mass: the number of atoms of each element is the same on the reactant side and on the product side.
Chemical reactions rearrange atoms — they never create or destroy them. If an equation shows 4 hydrogen atoms becoming 6, something is wrong. The coefficients (numbers before formulas) tell you how many molecules or moles of each substance participate, and they must be chosen so the total atom count is conserved.
Types of Chemical Reactions
Most chemical reactions fall into one of five categories. Each has a characteristic shape that can help you balance it faster.
| Type | General Form | Example |
|---|---|---|
| Synthesis (combination) | A + B → AB | 2H₂ + O₂ → 2H₂O |
| Decomposition | AB → A + B | 2H₂O → 2H₂ + O₂ |
| Single replacement | A + BC → AC + B | Zn + 2HCl → ZnCl₂ + H₂ |
| Double replacement | AB + CD → AD + CB | NaOH + HCl → NaCl + H₂O |
| Combustion | CₓHᵧ + O₂ → CO₂ + H₂O | CH₄ + 2O₂ → CO₂ + 2H₂O |
Practice Worksheet
Test your balancing skills with 80 equations across 4 difficulty levels — from simple synthesis to complex redox. Enter coefficients, check your answers instantly, and see solutions step by step.
Frequently Asked Questions
How do you balance a chemical equation?
By adjusting the coefficients (numbers in front of formulas) — not the subscripts — until each element has equal atom counts on both sides. This calculator uses Gaussian elimination to find the smallest integer coefficients automatically.
What does balancing a chemical equation mean?
It means applying the law of conservation of mass: the number of atoms of each element must be the same on the reactant side and on the product side. Matter cannot be created or destroyed in a chemical reaction.
Can you change subscripts to balance an equation?
No. Changing subscripts changes the compound itself — H₂O and H₂O₂ are different substances (water vs. hydrogen peroxide). Only coefficients (numbers before formulas) can be changed when balancing.
What if my equation cannot be balanced?
Some equations represent reactions that do not actually occur, or are missing a species. If the balancer returns an error, verify that every element on one side also appears on the other, and check for typos in the chemical formulas (case matters: Co is cobalt, CO is carbon monoxide).
What are coefficients in a chemical equation?
Coefficients are the numbers placed before chemical formulas to indicate the relative amount (number of moles) of each substance. In 2H₂O, the coefficient is 2 — meaning two molecules (or two moles) of water.
How does this calculator balance equations?
It converts the equation into a system of linear equations (one per element), then applies Gaussian elimination to find the null space of the coefficient matrix. The resulting vector is scaled to the smallest positive integers, giving the balanced coefficients.
How many equations should I practice to learn balancing?
Start with the 5 easy equations (synthesis and decomposition with 2 compounds), then progress to medium (combustion, single replacement) and hard (neutralization, multi-product). Most students feel confident after balancing 15–20 equations covering different reaction types. See the practice worksheet below for a graded set.
Related Chemistry Tools
- Molar Mass Calculator — once the equation is balanced, calculate the molar mass of each species.
- Empirical Formula Calculator — find the empirical or molecular formula of a compound.
- Molarity Calculator — compute solution molar concentration from mass and volume.
- Grams to Moles Calculator — convert mass to moles using molecular weight.
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This tool applies the law of conservation of mass and uses Gaussian elimination over the element-coefficient matrix to find balanced equations. Atomic data sourced from IUPAC 2021 standard atomic weights.
