Empirical Formula Helper — mole ratio from percent composition

An empirical formula is the simplest whole-number ratio of atoms in a compound. This helper converts the mass percents of two elements into their mole ratio — divide each percent by its atomic mass, then divide both results by the smaller one and round to whole numbers.

Empirical Formula Helper — mole ratio from percent composition

$mole\ ratio = \frac{\%A / A_A}{\%B / A_B}$

Solve for

Mass percent of element A (%A)

Unit

Atomic mass of A (A_A)

Unit

Mass percent of element B (%B)

Unit

Atomic mass of B (A_B)

Unit

Result unit

How to interpret the result

Worked check: H 11.19%, O 88.81% → (11.19/1.008)/(88.81/15.999) = 11.101/5.551 = 2.00, so H:O = 2:1 and the empirical formula is H₂O. Ratios like 1.5 or 2.5 mean you should double everything (e.g. 1.5 → 3:2).

Assumptions

Binary compound (two elements); extend the same math for more
Percents refer to the same sample
Final rounding to whole numbers is a chemical judgment, not pure math