What is the Molecular Formula Calculator?
The molecular formula gives the actual number of each atom in a molecule. It is always a whole-number multiple of the empirical formula. This calculator finds n = experimental molar mass ÷ empirical formula mass, then outputs the molecular formula. Enter an empirical formula (e.g. CH₂O) plus experimental molar mass (e.g. 180.16 g/mol for glucose → C₆H₁₂O₆), or provide elemental composition and molar mass in one step. Uses standard atomic weights. Runs instantly in your browser with no signup.
How to use the Molecular Formula Calculator
- Choose empirical formula + molar mass, or composition + molar mass.
- Enter the empirical formula or element composition values.
- Enter the experimental molar mass in g/mol.
- Read the multiplier n, empirical formula, and molecular formula.
- Copy the summary for homework or lab reports.
Common use cases
- Getting C₆H₁₂O₆ from empirical CH₂O and molar mass 180.16 g/mol
- Finding C₆H₆ from empirical CH and molar mass 78.11 g/mol (benzene)
- One-step molecular formula from mass % and experimental molar mass
Frequently asked questions
- How is molecular formula calculated?
- n = M(experimental) / M(empirical). Molecular formula = empirical formula × n. For glucose, CH₂O (30 g/mol) and M = 180 g/mol gives n = 6, so C₆H₁₂O₆.
- What if n is not a whole number?
- n should be an integer. A non-integer ratio usually means incorrect empirical formula, wrong molar mass, or impure sample. The calculator warns when n is not close to a whole number.
- Can I enter composition directly?
- Yes — use composition + molar mass mode. The tool finds the empirical formula from your data, then applies the molar mass multiplier.
- How is this different from empirical formula?
- Empirical formula is the simplest ratio (CH₂O). Molecular formula is the true atom count (C₆H₁₂O₆) — you need experimental molar mass to find it.
