Type an equation below and get a step-by-step guide that explains every coefficient — not just the final answer.
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Type the equation using plain text. Use element symbols (e.g. H2, O2, NaOH, CH4). You can write the arrow as → or just separate reactants from products with a space — the tool understands both.
Your balanced equation and step-by-step explanation will appear here. Click an example above or type your own equation, then click "Balance It".
Balancing equations is one of those topics that looks confusing at first but becomes very straightforward once you follow a clear system. Here is the method that experienced chemistry students use.
A coefficient is the big number in front of a formula, like the 2 in 2H₂O. A subscript is the small number inside the formula, like the 2 in H₂O. You can only change coefficients — never subscripts. Changing subscripts changes the substance itself (H₂O is water, H₂O₂ is hydrogen peroxide — completely different things).
In any chemical reaction, atoms are not created or destroyed — they are just rearranged. So the number of each type of atom on the left side (reactants) must equal the number on the right side (products). This is the whole point of balancing.
Follow this order and you will balance most equations correctly on the first try: metals first → non-metals next → hydrogen → oxygen last. The reason for this order is that O and H appear in more compounds than other elements, so balancing them last gives you more flexibility.
If you end up with an odd number of atoms on one side from a diatomic molecule (like O₂), use the Lowest Common Multiple (LCM). For example, if you need 3 O on the left but O₂ gives you 2 at a time — use 3 × O₂ to get 6, then balance the right side to 6 as well. It sounds complex but becomes second nature quickly.
Once you think the equation is balanced, go through every element one more time and count atoms on both sides. Never skip this step in an exam — it takes 20 seconds and protects marks you have already earned.
Exam Tip: In O Level Chemistry, show your atom count in a small table next to the equation. Examiners can then see your working even if you make a minor arithmetic error, and you can still earn method marks.
A fuel reacts with oxygen to produce carbon dioxide and water. The pattern is always: fuel + O₂ → CO₂ + H₂O. Balance C first, then H, then O. Combustion reactions are the most common type in exams.
An acid reacts with a base to produce a salt and water. The general formula is: Acid + Base → Salt + Water. Many neutralisation equations are already balanced or need only small coefficients.
Two or more substances combine to form a single product. The Haber process (N₂ + 3H₂ → 2NH₃) is a classic example and a favourite in O Level exams.
A substance reacts with oxygen, often gaining oxygen atoms. Rusting (iron + oxygen → iron oxide) is an oxidation reaction you will almost certainly see in your exam.