Overview
What Is Percent Composition?
Percent composition shows what percentage of a compound's total mass comes from each element, calculated from the molecular formula.
Calculate percent composition of a compound.
Percent composition shows what percentage of a compound's total mass comes from each element, calculated from the molecular formula.
Useful for understanding compound composition and stoichiometry coursework.
Input the mass this element contributes based on its count in the formula.
Input the compound's total molecular weight.
The result updates automatically.
Percent Composition = (Element's Total Mass in Formula ÷ Total Molecular Weight) × 100
Multiply the element's atomic weight by how many atoms of it appear in the formula.
Yes, the percentages of all elements in a compound should sum to 100%.
Use our molecular weight calculator to sum all atomic weights in the formula.
Yes, percent composition data is commonly used to work backward to determine empirical formulas.
No, calculations happen entirely in your browser.
Yes, comparing calculated vs experimental percent composition can help verify or identify compounds.
Yes, hydrated compounds (with water molecules attached) have different percent composition than anhydrous forms.
Yes, percent composition matters in pharmaceutical formulation, agriculture (fertilizer content), and materials science.
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