Convert all given masses (or percentages) to moles
If given mass: divide each element’s mass by its atomic mass to get moles
If given percentages: assume 100 g total, then divide each element’s mass (percent) by its atomic mass to get moles
Divide all mole values by the smallest mole value to get the simplest whole-number ratio
If ratios are not whole numbers, multiply all ratios by the smallest factor (2, 3, 4, etc.) to make them whole numbers
Round to the nearest whole numbers if close
Write the empirical formula using the whole-number ratios as subscripts
If a ratio simplifies further (common factor), reduce to the lowest whole-number ratio
If given a molecular formula: divide subscripts by the empirical subscripts to find the multiplier (optional)