Percent Composition Calculator

Find an element's mass percentage in a compound.

Percent composition (%) 88.815

Formula: percent = element mass ÷ total mass × 100

Step-by-step with your numbers:

1. Values used:

2. Element mass = 16 g/mol

3. Compound molar mass = 18.015 g/mol

5. Percent composition = 88.815%

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The mass fraction of an element within a compound.

The math behind it

percent = (mass of element ÷ molar mass of compound) × 100.

Oxygen in water: 16 ÷ 18.015 = 88.8%.

Multiple atoms?

Multiply the atomic mass by how many of that atom are in the formula.