Empirical Formula Calculator

Turn percent composition or mass data into the simplest whole number formula.

Empirical formula from composition

Type of data

One element per line, symbol then value

Empirical formula: —

Mole ratio: —

Formula mass: —

Status: —

Atomic masses for all 118 elements are built in, so the formula is found without any network access.

Common questions about the free online empirical formula calculator.

It is the simplest whole number ratio of the atoms in a compound. Glucose, C6H12O6, has the empirical formula CH2O.

Assume 100 g of sample, divide each percentage by the atomic mass to get moles, then divide every value by the smallest one.

If a ratio is close to a fraction such as 0.5, multiply every value by two, or by three for thirds, until all are whole numbers.

Yes. Switch the data type to mass in grams and enter the mass of each element in the sample; the arithmetic is exactly the same.

Those percentages give a one to two to one ratio, so the empirical formula is CH2O with a formula mass of about 30.03.

The molecular formula is a whole number multiple of the empirical formula, found by dividing the molar mass by the formula mass.

No. The atomic masses are built into the page and every calculation runs locally in your browser.

Yes. The calculator is responsive and works on phones, tablets and desktop browsers with nothing to install.

Last updated: October 10, 2026