Empirical Formula Calculator

Find the simplest whole-number ratio of elements from mass or percent composition.

Empirical Formula Calculator

Find the simplest whole-number ratio of elements from mass or percent composition.

Formula
Divide each mole value by the smallest, then round to nearest whole numbers
What is This Tool?

The empirical formula represents the simplest whole-number ratio of atoms of each element in a compound. It is determined by converting masses to moles, dividing by the smallest mole value, and rounding to whole numbers. The molecular formula is a whole-number multiple of the empirical formula.

Formula
1. Convert mass of each element to moles: n = mass / molar mass 2. Divide each by the smallest mole value 3. Round to nearest whole numbers 4. These are the subscripts in the empirical formula
Worked Examples

1. Compound with C and H

Given: 40.0 g C (12.01 g/mol), 6.7 g H (1.008 g/mol)

mol C = 40.0 / 12.01 = 3.33

mol H = 6.7 / 1.008 = 6.65

Divide by smallest (3.33): C = 1, H = 2

Result: Empirical formula: CH2

2. Compound with Na and Cl

Given: 46.0 g Na (22.99 g/mol), 71.0 g Cl (35.45 g/mol)

mol Na = 46.0 / 22.99 = 2.00

mol Cl = 71.0 / 35.45 = 2.00

Ratio = 1 : 1

Result: Empirical formula: NaCl

Frequently Asked Questions