Empirical Formula Calculator

Find the simplest whole number formula of a compound from element masses or percentages.

Enter one element per line as symbol and mass, for example: C 40.0. Use grams or percentages, the math is the same.

Percentages (%) Mass in grams (g)

Elements and amounts

Empirical Formula

Mole Steps

Element	Amount	Atomic mass	Moles	Divide by smallest

How It Works

Divide each mass by the atomic mass to get moles. Divide every mole value by the smallest one. Round to whole numbers. Those whole numbers are the subscripts in the empirical formula.

Moles = Mass / Atomic mass

Worked example, glucose data: C 40.0%, H 6.7%, O 53.3%. Moles: 40.0 / 12.011 = 3.33 mol C, 6.7 / 1.008 = 6.65 mol H, 53.3 / 15.999 = 3.33 mol O. Divide by the smallest (3.33): C 1, H 2, O 1. The ratio is 1:2:1, so the empirical formula is CH2O.

Atomic Masses Used (IUPAC standard atomic weights)

Hydrogen (H)

1.008

Carbon (C)

12.011

Nitrogen (N)

14.007

Oxygen (O)

15.999

Sodium (Na)

22.990

Magnesium (Mg)

24.305

Sulfur (S)

32.06

Chlorine (Cl)

35.45

Calcium (Ca)

40.078

Iron (Fe)

55.845

Frequently Asked Questions

An empirical formula calculator finds the simplest whole number ratio of atoms in a compound. Enter each element with its mass in grams or its percentage, and it works out the moles of each element, divides by the smallest value, and gives the formula.

Treat the percentages as grams in a 100 g sample. Divide each mass by the atomic mass to get moles, divide all mole values by the smallest one, then round to whole numbers. Those whole numbers are the subscripts in the formula.

Glucose has the molecular formula C6H12O6. Its percentage data is C 40.0%, H 6.7%, O 53.3%, which gives moles of 3.33, 6.65 and 3.33, a ratio of 1:2:1, and the empirical formula CH2O.

The empirical formula is the simplest whole number ratio of atoms. The molecular formula is the real number of atoms in one molecule, and it is a whole number multiple of the empirical formula.

It uses standard IUPAC atomic weights: H 1.008, C 12.011, N 14.007, O 15.999, Na 22.990, Mg 24.305, S 32.06, Cl 35.45, Ca 40.078, Fe 55.845.

Multiply all ratios by a small whole number (2, 3, 4, 5 or 6) until every value is close to a whole number. For example a ratio of 1 to 1.5 becomes 2 to 3.

Yes. Enter the mass of each element in grams and the tool does the same steps. The numbers work the same way whether you enter grams or percentages.

Related Tools

Periodic Table

Browse every element with atomic mass, number, and properties.

Peptide Calculator

Work out peptide doses and reconstitution volumes.

Boiling Point of Metals

Look up the boiling point of any metal in seconds.

Was this tool helpful?

Comments

Loading comments...

Check Out Other Popular Tools

Chinese Tones Quiz — Master the 4 Mandarin Tones

Free 20-question quiz on the four Mandarin tones, the neutral tone and tone-change rules (sandhi). Instant feedback with an explanation for every answer.

Education55

Variance Calculator

Calculate Population Variance, Sample Variance, Standard Deviation, and Mean instantly. Get step-by-step explanations for your data set.

Math Tools699

Calculatrice Hypothécaire Suisse

Calculez votre prêt immobilier en Suisse. Vérifiez votre tenabilité (affordability) avec le taux théorique de 5% et le ratio de nantissement (LTV).

Calculators486