Empirical to Molecular Formula Calculator
An empirical formula tells you the simplest ratio of atoms in a compound, but it does not tell you how many atoms are actually in a single molecule. Glucose, for instance, has the empirical formula CH2O, yet a real glucose molecule is six of those units stacked together as C6H12O6. The bridge between the two is a single whole number, the multiplier n, and this calculator finds it for you. The principle is straightforward: the molecular weight of the real compound is always a whole-number multiple of the weight of one empirical unit, so dividing the molecular weight by the empirical formula weight reveals exactly how many units there are. Enter the measured molecular weight and the empirical formula weight you calculated from atomic masses, and the tool returns the raw ratio along with the nearest whole-number multiplier, which you then apply to every subscript in the empirical formula. Because measured weights carry small rounding errors, the raw ratio will sit close to an integer rather than exactly on it, and rounding gives the answer. Every figure is computed deterministically, with a worked example below that reconciles exactly to the calculator so you can check the arithmetic.
The molecular formula is a whole-number multiple of the empirical formula: n = molecular weight / empirical formula weight. For a molecular weight of 180.16 and an empirical (CH2O) weight of 30.026, n is 6.00, so CH2O becomes C6H12O6 (glucose).
Empirical to molecular formula formula
n = molecular weight / empirical formula weight
molecular formula = (empirical formula) with each subscript x n
molecular weight = mass of one mole of the real compound
empirical formula weight = sum of atomic weights in the simplest ratio
Dividing the molecular weight by the empirical formula weight gives the number of empirical units per molecule. Round that ratio to the nearest whole number to get n.
Worked example
A compound has empirical formula CH2O (formula weight 30.026 g/mol) and a measured molecular weight of 180.16 g/mol.
- Raw ratio = 180.16 / 30.026 = 6.000.
- Round to the nearest whole number: n = 6.
- Multiply each subscript in CH2O by 6: C6H12O6.
- The molecular formula is C6H12O6 (glucose).
These are the calculator's default inputs, so the result above matches the widget exactly.
Empirical to molecular formula calculator: frequently asked questions
What is the difference between empirical and molecular formulas?
An empirical formula gives the simplest whole-number ratio of atoms in a compound, such as CH2O. The molecular formula gives the actual number of each atom in one molecule, such as C6H12O6 for glucose. The molecular formula is always a whole-number multiple of the empirical formula.
How do I find the multiplier n?
Divide the molecular weight, measured for the real compound, by the empirical formula weight, calculated from the simplest ratio. The result should be a whole number. That whole number, n, is how many empirical units make up one molecule, so you multiply every subscript in the empirical formula by n.
What if the multiplier is not a whole number?
It should be very close to an integer. A small deviation comes from rounding in the molecular or empirical weights, so round to the nearest whole number. A large deviation usually means an error in the empirical formula or the measured molecular weight, and you should recheck both before proceeding.
Where does the molecular weight come from?
The molecular weight is typically determined experimentally, for example by mass spectrometry or freezing-point depression. The empirical formula weight is computed by adding the standard atomic weights of the atoms in the empirical formula, using values published by the National Institute of Standards and Technology.
What is the empirical to molecular formula formula?
n equals the molecular weight divided by the empirical formula weight, rounded to the nearest whole number. The molecular formula is then the empirical formula with every subscript multiplied by n. For glucose, 180.16 divided by 30.026 is about 6, so CH2O becomes C6H12O6.
Official sources
- Standard atomic weights for computing formula weights: US National Institute of Standards and Technology (NIST). As at 25 June 2026.
Reviewed by the CalculatorHub team, edited by James Graham, 25 June 2026. See our methodology. This is general information, not financial, tax, legal or investment advice.