Free tool · shows working
Chemical equation balancer
Balances the equation and shows how. Handles brackets, polyatomic ions and hydrates, and prints an atom count for every element so you can check the result rather than trust it.
Write it as you would by hand. Use -> for the arrow and + between species. Brackets and hydrates both work: Al2(SO4)3, CuSO4·5H2O.
Try one
Working
- Elements involved: C, H, O. Unknowns: 4 coefficients.
- Write one conservation equation per element — atoms in must equal atoms out.
- Solve the system. 4 unknowns and 3 independent equations leaves one free variable, which is why coefficients are a ratio.
- Scale the ratio to the smallest whole numbers: 1 : 5 : 3 : 4.
- Check: every element now has equal atom counts on both sides.
Balanced equation
C3H8 + 5O2 → 3CO2 + 4H2O
Atom check
| Element | Left | Right |
|---|---|---|
| C | 3 | 3 |
| H | 8 | 8 |
| O | 10 | 10 |
Runs entirely in your browser — nothing is uploaded. Coefficients are solved over exact fractions rather than decimals, so ratios like 1:3 do not drift.
Short answer
How do you balance a chemical equation?
Balance the elements that appear in only one reactant and one product first, then work outward, leaving oxygen and hydrogen until last because they usually appear in several species. If a coefficient comes out fractional, multiply every coefficient through to clear it. Never change a subscript — that changes the substance rather than the quantity. Finish by counting every element on both sides, and add the states of matter.
Frequently asked questions
- How do you balance a chemical equation?
- Balance elements that appear in only one reactant and one product first, leave oxygen and hydrogen until last, and use a fraction temporarily if it helps, then multiply through to clear it. Always add the states of matter — markers deduct for their absence.
- Why can't I change the subscripts?
- Subscripts define the substance. Changing H2O to H2O2 does not balance the equation, it replaces water with hydrogen peroxide. Only the coefficients in front of a formula may change.
- What if the coefficients come out as fractions?
- That is normal in combustion equations. Multiply every coefficient through by the denominator to clear it — this balancer does that automatically and shows the ratio it started from.
- Why does this equation say it cannot be balanced?
- Usually because an element appears on only one side, which means a formula is wrong or a species is missing. The tool names the element so you can find the typo.