Percent Composition Calculator

About this calculator

Percent composition (mass percent) is simply (part / total) × 100 — the mass of one component divided by the total mass of the mixture or compound. In chemistry, it's most often used to describe the percentage by mass of each element within a compound, calculated from the elements' molar masses relative to the compound's total molar mass, though the same math applies just as well to mixture purity or ingredient proportions.

Chemistry students use percent composition to verify empirical formulas from experimental mass data, analytical chemists use it to report purity of a sample or product, food scientists use it to calculate nutrition-label percentages, and pharmacists use it when formulating mixtures to hit a target concentration by mass. Enter the component mass and total mass to get the percentage.