Empirical to Molecular Formula Calculator
Find how many empirical units make up the molecular formula by dividing the molecular molar mass by the empirical formula mass.
How it works
n = molecular molar mass ÷ empirical formula mass (rounded to the nearest whole number) · Molecular formula = (empirical)ₙ
The empirical formula gives the smallest whole-number ratio of atoms, but the true molecule can be a whole-number multiple of it. Dividing the measured molecular molar mass by the empirical formula mass gives that multiplier, which must round to a whole number — a ratio far from an integer signals an error in the molar mass or the empirical formula. Multiplying every subscript in the empirical formula by n then yields the molecular formula.
Worked example
Glucose has the empirical formula CH₂O (mass 30.03 g/mol) and a measured molar mass of 180.16 g/mol. n = 180.16 ÷ 30.03 = 6.00, so the molecular formula is (CH₂O)₆ = C₆H₁₂O₆.
Sources: Empirical formula — Wikipedia
Frequently asked questions
What is the difference between empirical and molecular formula?
The empirical formula is the simplest whole-number ratio of atoms (CH₂O), while the molecular formula gives the actual atom counts in one molecule (C₆H₁₂O₆). The molecular formula is always the empirical formula multiplied by a whole number.
What if the ratio is not close to a whole number?
A ratio like 5.4 usually means either the empirical formula or the molar mass is slightly off. Re-check the percent composition and the molar-mass measurement; the true multiplier must be a whole number.
How do I get the molecular formula from n?
Multiply every subscript in the empirical formula by n. If the empirical formula is CH₂O and n = 6, the molecular formula is C₆H₁₂O₆.
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This calculator is for educational purposes. Double-check important results before acting on them.