Percentage composition of a compound is the number of parts by mass of each element in one hundred parts by mass of the compound. The percent by mass of each element in a compound is calculated using the relation:

To determine the percentage composition of a compound, we use the following steps.

1. Identify the elements and the number of atoms of each kind present in the compound.
2. Calculate the total mass of each element by multiplying its number in the formula of the compound with the respective molar mass.
3. Calculate the molar mass of the compound.
4. Calculate the percentage composition of the compound by dividing the total mass of each element by the molar mass of the compound and then multiply by 100.