Toolbox

A formula sheet plus reference tools for calculator, equation solver, units, elements, graphs and molecules.

Toolbox · Chemical Equation Balancer

Chemical Equation Balancer

Balance reactants and products automatically, parentheses and hydrates supported

Enter the equation (reactants = products)

Examples

Balanced equation

2\mathrm{H_{2}} + \mathrm{O_{2}}\ \longrightarrow\ 2\mathrm{H_{2}O}

2H₂

1O₂

2H₂O

ElementBeforeAfterCheck

H44✓

O22✓

Molar massesH₂ = 2.02O₂ = 32.00H₂O = 18.02

Balancing strategy

7 / 7

1Equation
$\mathrm{H_{2}} + \mathrm{O_{2}}\ \longrightarrow\ \mathrm{H_{2}O}$
Write reactants and products; both sides must contain the same elements.
2Atom count
$\text{H}: 2 \ne 2,\quad \text{O}: 2 \ne 1$
Count atoms of each element before balancing — usually the two sides differ.
3Coefficients
$\text{设系数 } a, b, c\text{，得}\quad a\mathrm{H_{2}} + b\mathrm{O_{2}} + c\mathrm{H_{2}O}$
Assign an unknown coefficient to every substance; balancing means finding them.
4Equations
$\text{H: } 2a = 2c\qquad \text{O: } 2b = 1c$
For each element, "atoms before = atoms after" gives a homogeneous linear system.
5Solve
$\text{解得 } a:b:c=2:1:2$
Solving gives a ratio, possibly with fractions.
6Simplify
$\gcd(2,1,2)=1$
Reduce the ratio to the simplest whole numbers.
7Check
$H: 4=4,\quad O: 2=2$
Every element now has equal atoms on both sides — balanced.

Concept

Balancing follows conservation of mass: the number of atoms of each element must be equal before and after.

Common methods are inspection, lowest common multiple, odd-even and oxidation-number methods. This tool solves a linear system, so any balanceable equation yields the simplest integer ratio.

Going further

Why the simplest ratio: An equation expresses a particle ratio: 2H₂ + O₂ → 2H₂O and 4H₂ + 2O₂ → 4H₂O describe the same reaction, so the simplest integers are used.
Ionic equations: Ionic equations also conserve charge. This tool handles molecular equations only; ionic ones need charge balancing as well.
Typical results: For example C₃H₈ + 5O₂ → 3CO₂ + 4H₂O and 2KMnO₄ + 16HCl → 2KCl + 2MnCl₂ + 5Cl₂ + 8H₂O.

Common mistakes

Coefficients go in front of a formula; never change the subscripts inside it.
Everything inside brackets is multiplied by the subscript outside: Ca(OH)₂ has 2 O and 2 H.
Always re-check every element afterwards — it is the easiest place to slip.

Page keywordsbalance chemical equationsequation balanceratom conservationstoichiometrybalance equations onlineequations with parenthesesbalancing steps explainedatom count checkcombustion of propane balancing

Related tools