Empirical Formula Calculator
Element Percentages
Enter each element and its mass percentage in the compound.
Enter element symbols and their mass percentages to find the empirical formula.
What is an Empirical Formula?
The empirical formula represents the simplest whole-number ratio of atoms in a compound. It does not tell you how many atoms are actually present, but rather the ratio between them.
For example, glucose has the molecular formula C₆H₁₂O₆, but its empirical formula is CH₂O (a 1:2:1 ratio).
How to Calculate Empirical Formula
- Convert percentages to grams (assume 100g sample).
- Convert grams to moles using atomic masses.
- Divide all mole values by the smallest mole value.
- Round to the nearest whole numbers (multiply if needed).
Examples
Example: Finding CH₂O
A compound is 40% C, 6.7% H, and 53.3% O.
- C: 40/12 = 3.33 mol
- H: 6.7/1 = 6.7 mol
- O: 53.3/16 = 3.33 mol
- Ratio: 3.33/3.33 : 6.7/3.33 : 3.33/3.33 = 1:2:1
- Empirical Formula: CH₂O
Empirical vs Molecular Formula
The molecular formula shows the actual number of atoms. The molecular formula mass is a whole-number multiple of the empirical formula mass.
For example, CH₂O (empirical, 30 g/mol) can become C₂H₄O₂ (acetic acid, 60 g/mol) or C₆H₁₂O₆ (glucose, 180 g/mol).
Frequently Asked Questions
What if percentages don't add to 100%?
The remaining percentage is often oxygen. Add O to make 100%.