Percent Composition Calculator

Percent Composition - Chemical Compound Calculation

Calculate percent composition percentage (%) using simple chemical compound calculator online.

Percent Composition (%) = (Total of Molar Mass Parts) / (Total of Whole Molar Mass) x 100

Note: The Law of Definite Proportions (Constant Composition) tells us that a compound has the same kinds of atoms in the same ratio.

Example: What is the percent composition of all elements in CH₃COOH?

1.Need molar mass of molecule.

2C = 2(12.0 g) = 24.0 g

4H = 4(1.0 g) = 4.0 g

2O = 2(16.0 g) = 32.0 g

Total = 60.0 g

Take the percentage of each element.

(i). % C = (24.0 / 60.0) * 100 = 40.0 %

(ii). % H = (4.0 / 60.0) * 100 = 6.67 %

(iii). % O = (32.0 / 60.0) * 100 = 53.3 %

40.0 % + 6.67 % + 53.3 % = 99.97 %

Composition of all elements in CH₃COOH is 99.97%.