Percent Composition Calculator

Calculate the percentage composition of elements by weight in chemical compounds using molecular formulas

Enter a valid chemical formula (case sensitive)

Leave blank to show all elements or specify one element symbol

Results

Element Percentage

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Molar Mass

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Element Mass in Formula

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Results Table

Frequently Asked Questions

What is percent composition?

Percent composition is the percentage by mass of each element in a chemical compound. It tells you what fraction of the total mass comes from each type of atom in the molecule.

How do I calculate the percent composition of a compound?

To calculate percent composition: 1) Find the molar mass of the compound, 2) Find the total mass of each element in the formula, 3) Divide each element's mass by the total molar mass and multiply by 100%.

What is the mass percentage of hydrogen in water?

In water (H2O), hydrogen makes up about 11.19% by mass. This is calculated as: (2 × 1.008) / (2 × 1.008 + 15.999) × 100% = 11.19%.

What is the percent composition of NaHCO₃?

In sodium bicarbonate (NaHCO₃): Sodium is 27.37%, Hydrogen is 1.20%, Carbon is 14.30%, and Oxygen is 57.14% by mass.

How much carbon is present in 100 g of sugar?

Sugar (C₁₂H₂₂O₁₁) contains about 42.1% carbon by mass, so 100g of sugar would contain approximately 42.1g of carbon.

Can I use this calculator for compounds with parentheses?

Yes, the calculator handles complex formulas including parentheses and nested structures like Al₂(SO₄)₃. Enter the formula exactly as written with proper capitalization.

Why is percent composition useful in chemistry?

Percent composition helps determine empirical formulas, verify compound purity, calculate how much of a specific element you get from a compound, and compare different compounds containing the same elements.

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