Empirical Formula Calculator
From percentages to formula, without rounding 1.5 to 2.
Work out Empirical Formula. From percentages to formula, without rounding 1.5 to 2. Shows the working, not just the answer.
Optional. Supply it to get the molecular formula as well.
Empirical formula
CH2O
Molecular formula: C6H12O6
Divide each mass by its atomic weight to get moles, divide all of those by the smallest, then scale to whole numbers. That last step is where this goes wrong by hand: a ratio of 1.5 must be doubled rather than rounded, because rounding turns Fe₂O₃ into FeO₂. The multiplier is searched here rather than assumed.
How the Empirical Formula Calculator works
Divide each mass by its atomic weight, divide those by the smallest, then scale to whole numbers. That last step is where this goes wrong by hand: a ratio of 1.5 must be doubled rather than rounded, because rounding turns Fe₂O₃ into FeO₂.
Also known as: molecular formula calculator · empirical formula from percent composition · how to find empirical formula · empirical to molecular formula
Frequently asked questions
How do I find an empirical formula?
Convert each percentage to moles by dividing by the atomic weight, divide everything by the smallest result, then multiply until all ratios are whole numbers. 40% C, 6.7% H and 53.3% O gives CH₂O.
How do I get the molecular formula?
Divide the known molecular mass by the empirical formula mass. For CH₂O at 30.03 g/mol against a molecular mass of 180.16, the multiplier is 6 — giving C₆H₁₂O₆, glucose.
What if the ratio is 1.33 or 1.5?
Multiply rather than round. 1.5 needs doubling and 1.33 needs tripling. This page searches for the smallest multiplier that makes every ratio whole, up to six, rather than rounding each one independently.
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