Empirical Formula Calculator
Derive the simplest whole-number formula from percentage composition.
About Empirical Formula Calculator
Assuming a 100 g sample turns mass percentages into grams directly. Dividing by atomic masses gives moles, and normalising by the smallest gives the atom ratio — 1:2:1 for glucose, hence CH₂O. The empirical formula is a ratio only; the molecular formula is a whole-number multiple of it, which requires the molar mass to determine.
Formula
Empirical Formula
Divide each mass percent by its atomic mass, then divide all results by the smallest
- empirical formula
- Simplest whole-number ratio of atoms, which may not be the molecular formula
Worked example
With the default values below, Empirical Formula Calculator returns Relative Atoms of Element 1 of 1.0000. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Mass percent of element 1accepts 0–100 %
- 40 %
- Atomic mass of element 1minimum 0 g/mol
- 12.011 g/mol
- Mass percent of element 2accepts 0–100 %
- 6.7 %
- Atomic mass of element 2minimum 0 g/mol
- 1.008 g/mol
- Mass percent of element 3accepts 0–100 %
- 53.3 %
- Atomic mass of element 3minimum 0 g/mol
- 15.999 g/mol
Results
- Relative Atoms of Element 1
- 1.0000
- Relative Atoms of Element 2
- 1.9959
- Relative Atoms of Element 3
- 1.0004
- Empirical Formula Mass
- 30.0275 g/mol
- Smallest Mole Value Used to Normalise
- 3.330281
Step by step
- 1Values used
- 2Empirical Formula
- 3Relative Atoms of Element 1= 1.0000
- 4Relative Atoms of Element 2= 1.9959
- 5Relative Atoms of Element 3= 1.0004
- 6Empirical Formula Mass= 30.0275 g/mol
- 7Smallest Mole Value Used to Normalise= 3.330281
Assumptions and limits
- The result is derived only from the 6 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 6 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is Empirical Formula calculated?
Divide each mass percent by its atomic mass, then divide all results by the smallest Assuming a 100 g sample turns mass percentages into grams directly. Dividing by atomic masses gives moles, and normalising by the smallest gives the atom ratio — 1:2:1 for glucose, hence CH₂O.
Why does Empirical Formula matter?
The empirical formula is a ratio only; the molecular formula is a whole-number multiple of it, which requires the molar mass to determine.
What values do I need to enter?
This calculator takes 6 inputs: Mass percent of element 1, Atomic mass of element 1, Mass percent of element 2, Atomic mass of element 2, Mass percent of element 3, Atomic mass of element 3. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.