Enter your Empirical Formula and Molecular Mass, choose your Calculation Type, and the Molecular Formula Calculator works out your Molecular Formula along with the Empirical Formula Mass, Multiplier (n), and a full Percent Composition breakdown for each element.
Molecular Formula
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Empirical Formula Mass
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Multiplier (n)
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Percent Composition
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The empirical formula shows the simplest whole number ratio of atoms in a compound, while the molecular formula shows the actual number of atoms of each element in a molecule. For example, glucose has empirical formula CH2O but molecular formula C6H12O6.
First, calculate the empirical formula mass. Then divide the molecular mass by the empirical formula mass to get the multiplier (n). Finally, multiply each subscript in the empirical formula by this multiplier to get the molecular formula.
You need two pieces of information: the empirical formula (simplest ratio) and the molecular mass (molar mass) of the compound. With these, you can determine the exact molecular formula.
Yes, when the molecular formula is already in its simplest form, it will be the same as the empirical formula. Examples include water (H2O), carbon dioxide (CO2), and methane (CH4).
For most calculations, molecular mass accurate to 2-3 decimal places is sufficient. However, more precise values will give more accurate results, especially when dealing with large molecules or precise analytical work.
If the multiplier is very close to a whole number (within 0.1), round to the nearest integer. If it's significantly different, check your empirical formula and molecular mass values for accuracy, as experimental error might be affecting your results.