Chemical Equation Balancer
Type an unbalanced equation and Calvo returns the smallest whole-number coefficients, with an atom-by-atom check so you can see that both sides match.
Balance a chemical equation
Use = or -> between the two sides and + between compounds. Capital letters matter: Co is cobalt, CO is carbon monoxide.
How to balance a chemical equation
A balanced equation has the same number of atoms of every element on both sides, because atoms are never created or destroyed in a reaction (law of conservation of mass). You balance it by changing the coefficients (the big numbers in front of formulas) and never the small subscripts.
- Write the unbalanced equation with correct formulas.
- Count the atoms of each element on both sides.
- Start with the element that appears in the fewest compounds, and leave hydrogen and oxygen for last.
- Adjust coefficients until every element matches. Use the smallest whole numbers.
- Count again to check.
Worked example: burning propane
Unbalanced: C3H8 + O2 → CO2 + H2O. Carbon: 3 on the left, so put 3 in front of CO2. Hydrogen: 8 on the left, so put 4 in front of H2O. Oxygen on the right is now 3 × 2 + 4 = 10, so put 5 in front of O2.
C3H8 + 5O2 → 3CO2 + 4H2O
How Calvo does it
Calvo writes one atom-balance equation for every element and solves them exactly with fractions, then scales to the smallest whole numbers and checks every element again before showing the answer. It accepts brackets such as Al2(SO4)3, hydrates such as CuSO4·5H2O (typed CuSO4.5H2O), and ignores state symbols like (s), (l), (g), (aq).
What this balancer cannot do
It balances by atoms only. Equations that need electron balance with charges (ionic half-reactions such as Fe3+) are not supported, and it cannot tell you whether the reaction really happens. If an equation can be balanced in more than one way, Calvo says so instead of guessing.
FAQ
How do I balance a chemical equation?
Count the atoms of each element on both sides and change the coefficients (not the subscripts) until all counts match, using the smallest whole numbers. Or type the equation into the balancer above.
Can I use the arrow or equals sign?
Yes. Use = or -> between the reactants and products, and + between compounds. Example: Fe + O2 = Fe2O3.
Does it support brackets and hydrates?
Yes. Brackets like Ca(OH)2 and Al2(SO4)3 work, and hydrates can be typed as CuSO4.5H2O.
Why does it say an element appears on only one side?
Every element must appear on both sides of a balanced equation. Check the formulas for a typing mistake, for example Co (cobalt) typed instead of CO (carbon monoxide).
Why does it say there is more than one way to balance?
Some equations are really two reactions written together, so many coefficient sets work. Split them into separate reactions and balance each.
Is balancing by coefficients or subscripts?
Only by coefficients. Changing a subscript changes the substance, for example H2O becomes H2O2.
Does it work offline?
Yes. The calculation runs in your browser and the page is cached after your first visit.