Empirical Formula Calculator (Percent Composition)
Enter the percent by mass of each element and get the simplest whole-number empirical formula.
Result
Empirical Formula
CH2O
Sum of %
100.00%
OK
Scale factor used
× 1
Concept
The empirical formula is the simplest whole-number ratio of atoms in a compound. It may or may not equal the molecular formula — glucose (C₆H₁₂O₆) has empirical formula CH₂O.
The procedure: convert percent composition to moles by dividing by atomic mass, then divide all mole values by the smallest to get ratios. If the ratios aren't whole numbers, multiply by a small integer (2–6) until they are.
To find the molecular formula from the empirical formula: molecular formula mass ÷ empirical formula mass gives the multiplier n, and molecular formula = (empirical formula) × n.
Formula
Moles of element=% compositionAtomic mass
Ratio=Moles of each elementSmallest mole value
Scale if needed=Multiply all ratios by 2, 3, 4… until all are whole numbers
Variables
% composition- Mass percent of each element — should sum to ~100%.
Atomic massg/mol- Atomic weight from the periodic table.
Moles ratio- Moles of each element ÷ smallest moles value.
n- The multiplier to convert empirical → molecular formula, found from the known molecular mass.