What is percent composition?

Percent composition shows what percentage of a compound's total mass comes from each element. It's calculated as (mass of element ÷ molar mass) × 100%.

How do I calculate percent composition?

For each element: multiply atomic mass by subscript, divide by molar mass of compound, multiply by 100. All percentages should sum to 100%.

What's the difference between molecular and empirical formula?

Empirical formula shows the simplest ratio of elements (CH2O). Molecular formula shows actual atom counts (C6H12O6). Molecular formula is a multiple of empirical.

How do I find empirical formula from percent composition?

Assume 100g sample, convert percentages to grams, divide by atomic masses to get moles, then divide all by the smallest mole value.

Why is percent composition important?

It's used to verify compound identity and purity, determine unknown compound formulas, and perform stoichiometric calculations in chemistry.

Percent Composition Calculator

Calculate the percentage by mass of each element in a chemical compound

Input

Input Method

Chemical Formula

Enter formula with proper capitalization (e.g., NaCl not nacl)

Common Compounds:

Results

Enter a chemical formula or elements to calculate percent composition

How to Calculate Percent Composition

% Composition = (Mass of Element in Compound ÷ Molar Mass of Compound) × 100

Steps to Calculate

Find the molar mass of each element in the compound
Multiply by the number of atoms of that element
Add all masses to get total molar mass
Divide each element's mass by total and multiply by 100

Example: Water (H₂O)

H: 2 × 1.008 = 2.016 g/mol
O: 1 × 16.00 = 16.00 g/mol
Total: 18.016 g/mol
% H = (2.016 ÷ 18.016) × 100 = 11.19%
% O = (16.00 ÷ 18.016) × 100 = 88.81%

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About Percent Composition Calculator - Chemistry Tool

Calculate the percent composition of elements in chemical compounds. Find mass percentages and empirical formulas from molecular formulas.

Our **Percent Composition Calculator** determines the mass percentage of each element in a chemical compound. Enter a molecular formula to get detailed breakdowns showing how much each element contributes to the total mass. For pH calculations, try our pH Calculator.

Percent composition is fundamental in chemistry for understanding compound makeup, verifying purity, and converting between empirical and molecular formulas. This tool uses accurate atomic masses for precise calculations.

The calculator handles complex formulas with parentheses, subscripts, and hydrates. It's perfect for students learning stoichiometry or professionals needing quick composition analysis.

Key Features

Mass percentage calculation

Atomic mass breakdown

Common compound database

Formula validation

Empirical formula hints

Hydrate support

Why Use This Tool?

Quick chemistry calculations

Accurate atomic masses

Educational explanations

Laboratory reference tool

Stoichiometry helper

Common Use Cases

Chemistry Class: Learning stoichiometry concepts.

Lab Work: Verifying compound purity.

Research: Analyzing unknown samples.

Industry: Quality control calculations.

Related Tools

pH Calculator

Acid-base calculations.

Ideal Gas Law Calculator

Gas calculations.

How to Use

Enter the chemical formula (e.g., H2SO4)

Click Calculate

View mass percentages for each element

See total molar mass

Use results for stoichiometry problems