Balancing chemical equations

Type an unbalanced equation and this balances it, then shows the atom count for every element on both sides so you can see that it genuinely worked rather than taking the answer on trust.

Unbalanced equation

Separate substances with + and the two sides with = or ->. Leave the coefficients out; that is what this works out. Brackets and hydrate dots both work.

Why equations need balancing at all

Atoms are not created or destroyed in a chemical reaction. They get rearranged into different combinations, but every atom you start with has to appear somewhere at the end. A balanced equation is just that fact written down: the same count of each element on both sides.

The coefficients, the big numbers in front, are how you make the counts match. They tell you how many of each molecule take part.

The rule that matters most: you may only change the coefficients, never the subscripts. Changing H₂O to H₂O₂ does balance the oxygens, but it also changes water into hydrogen peroxide, which is a different substance entirely. Subscripts are part of the compound's identity.

How to balance by hand

Most school equations come out with a simple routine. Leave oxygen and hydrogen until last, because they usually appear in several compounds and shift around as you adjust the others.

Start with an element that appears in only one substance on each side, and balance that. Then work through the rest, saving oxygen and hydrogen for the end. If you finish with a fraction, such as 3/2 O₂, multiply every coefficient by the denominator to clear it, since coefficients are normally written as whole numbers.

Then count every element on both sides to check. That final count is the step people skip and the reason wrong answers slip through, so this tool always shows it.

Common questions

Can a coefficient be a fraction?: Mathematically yes, and you will sometimes see 1/2 O₂ used when balancing combustion equations, particularly at A-Level for enthalpy calculations where one mole of fuel matters. For a normal balanced equation, multiply through to clear the fraction so all coefficients are whole numbers.
What if my equation cannot be balanced?: Usually it means something is missing or misspelled. An element appearing on only one side can never balance, and a mistyped formula can quietly change the atom counts. This tool names the specific element that cannot be balanced rather than just failing.
Does the order of substances matter?: No. As long as each substance is on the correct side of the arrow, the order within a side makes no difference to the balancing.
How does this get the answer?: It treats the equation as a set of simultaneous equations, one per element, then solves them together and scales the result to the smallest whole numbers. That is more reliable than trial and error and works on equations that are painful to do by inspection.