Empirical and Molecular Formula Calculator
Turns a composition into a formula.
Share sends a link that reopens these numbers. Copy details pastes the full breakdown as a list.
The formula
moles = amount ÷ atomic weight ratio = moles ÷ smallest moles molecular formula = empirical formula × (molar mass ÷ empirical mass)
Percentages work directly, as if the sample weighed 100 g. Masses of any size work the same way.
What to watch out for
Compounds of carbon and hydrogen list carbon, then hydrogen, then the rest alphabetically. Other formulas list metals first, then non-metals in the usual order. An empirical formula has no brackets, so Ca(OH)₂ reads CaO₂H₂. Atomic weights are abridged.
Frequently Asked Questions
What is the difference between empirical and molecular formula?
The empirical formula is the simplest whole-number ratio, and the molecular formula is the real count. CH₂O and C₆H₁₂O₆ have the same ratio.
How do I get from 40% C, 6.7% H and 53.3% O to a formula?
Divide each by its atomic weight, then by the smallest result. The ratio is 1 : 2 : 1, so the formula is CH₂O, with an empirical mass of 30.03 g/mol.