About the Percent Composition Calculator
Percentage by mass of every element in a compound, with the mass of each in a sample.
Also known as: mass percent of element, percentage composition, elemental analysis, percent by mass.
How to use this calculator
- Enter chemical formula, sample mass.
- The result updates instantly as you type — press Calculate (or Enter) at any time.
- Review the breakdown shown under the main result.
- Use Copy result or Share to save the answer or send a link with your inputs.
Formula
% element = (atoms × atomic mass) / molar mass × 100
Worked example
Using the values pre-filled in the calculator above:
- Chemical formula: C6H12O6
- Sample mass = 100 g
the calculator returns:
- Largest component: O: 53.284 %
- Molar mass: 180.156 g/mol
- Elements: 3