Empirical Formula Calculator

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

Enter up to 5 elements and their mass percentages (must total ≈ 100%).

How It Works

Enter element symbols and their mass percentages. The calculator divides each percentage by the element's atomic mass to get mole ratios, then divides by the smallest ratio and rounds to find the empirical formula.

Formula

Divide % by atomic mass → find smallest mole ratio → multiply to whole numbers

Examples

H 5.9%, O 94.1% → H2O | C 40%, H 6.67%, O 53.3% → CH2O (formaldehyde)

Frequently Asked Questions

What is an empirical formula?

An empirical formula shows the simplest whole-number ratio of elements in a compound. For example, glucose (C6H12O6) has the empirical formula CH2O.

How do I convert percent composition to empirical formula?

Divide each element's mass percent by its atomic mass to get moles. Divide all mole values by the smallest. Round to whole numbers (multiply if needed).

When do I multiply to get whole numbers?

If any ratio ends in .5, multiply all by 2. If any ends in .33 or .67, multiply by 3. Continue until all are whole numbers.