Empirical Formula Calculator
Turn element mass percentages or grams into the simplest whole-number (empirical) formula.
How it works
moles = mass ÷ atomic mass · divide each by the smallest · scale to whole numbers
The empirical formula is the simplest whole-number ratio of atoms in a compound. Convert each element's mass (or mass percent) to moles by dividing by its atomic mass, divide every result by the smallest to get a ratio, then scale up until all values are whole numbers. Assuming a 100 g sample lets you use the percentages directly as grams.
Worked example
A compound of 40% C, 6.7% H and 53.3% O gives moles 40/12.011 = 3.33, 6.7/1.008 = 6.65, 53.3/15.999 = 3.33. Dividing by 3.33 gives 1 : 2 : 1, so the empirical formula is CH₂O.
Sources: Empirical formula — Wikipedia
Frequently asked questions
What is the difference between empirical and molecular formula?
The empirical formula is the simplest ratio (CH₂O); the molecular formula is the actual count of atoms (glucose is C₆H₁₂O₆, six times the empirical unit). You need the molar mass to go from one to the other.
Can I enter grams instead of percentages?
Yes. The method only uses ratios, so grams and mass percentages give the same empirical formula. Enter whichever you measured.
Why does it multiply by a factor?
Some ratios come out near 1.5 or 1.33 rather than whole numbers. Multiplying all of them by 2 or 3 clears the fraction and yields the smallest whole-number set of subscripts.
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