Chemical Equation Balancer
Adjust the coefficients yourself and watch the atom counts respond — this activity is built to teach the reasoning behind balancing, not just hand you the answer.
Balance the chemical equation
Change the coefficients until every element has the same number of atoms on both sides of the equation.
You can change coefficients, but never change the subscripts in a chemical formula.
Atom Count
Updates live as you change coefficients.
| Element | Reactants | Products | Status |
|---|---|---|---|
| Hydrogen | 2 | 2 | Balanced |
| Oxygen | 2 | 1 | Needs balancing |
What happens when coefficients change?
A coefficient multiplies every atom in that formula.
Molecule Groups
A schematic view of one unit of each substance — the ×N badge shows the coefficient.
Hints
Stuck? Hints get progressively more specific — try adjusting coefficients first.
Understanding Balanced Equations
How to Balance Chemical Equations
Balancing means adjusting the coefficients — the numbers placed in front of each formula — until every element has the same total number of atoms on the reactant and product sides. Work one element at a time: count its atoms on both sides, then change a coefficient to bring them closer, and re-check how that changed every other element in that formula.
Coefficient vs Subscript
A coefficient (the 2 in 2H₂O) sits in front of a formula and multiplies every atom inside it, without changing what the substance is. A subscript (the 2 in H₂O itself) is part of the formula and tells you how many atoms of that element are in one unit of the substance. Coefficients may change freely while balancing; subscripts must never change, because editing a subscript turns the substance into a completely different one.
Why Chemical Equations Must Be Balanced
The law of conservation of mass says matter is neither created nor destroyed in a chemical reaction — every atom present in the reactants has to show up somewhere in the products. A balanced equation is simply the bookkeeping that proves this: equal atom counts on both sides confirm no atoms were gained or lost during the reaction.
Practice Chemical Equations
The activity above includes beginner equations (simple combination and synthesis reactions), intermediate equations (combustion and decomposition with multiple products), and more challenging equations (polyatomic ions and multi-step reactions) — use Previous/Next to move between them at your own pace.