Worked example

40% C: 40/12=3.33 mol... → normalize.

Empirical Formula Relation

Determine simplest whole-number ratio from percent composition.

Equation

$\text{ratio}=\frac{\% /M}{smallest}$

Inline: $\text{ratio}=\frac{% /M}{smallest}$$

Variables

Symbol	Quantity	Unit	Notes
$$	percent element	%	—
$M$	atomic weight	g·mol⁻¹	—

Conditions and limitations

Assume 100 g sample when given percents.

Rearrangements

Multiply by integer to get whole numbers.

Dimensional check: mass/molar mass = mol ratio ✓

Worked example

40% C: 40/12=3.33 mol… → normalize.

Steps: write equation → substitute with units → check dimensional consistency → report with correct significant figures.

Common errors

• Rounding too early

Related resources

• mole-stoichiometry topic
• Calculators — linked only when a real calculator implements this formula.
• Constants — sourced constants with version when values are required.

Sources

• NIST Physical Constants 2022 — CODATA.

Reviewed 2026-08-21 by Editorial Team; due 2027-08-21.