Percent Composition Calculator – Find Mass Percent of Elements
Determine the percent composition by mass of each element in a compound with our free percent composition calculator. Enter the chemical formula and get accurate elemental percentages instantly. Perfect for chemistry coursework and analysis.
Percent composition shows the percentage by mass of each element in a compound. You calculate it by dividing the total mass of each element by the molar mass of the compound and multiplying by 100.
Percent Composition Formula
Steps to Calculate
- Find the molar mass of the compound
- Calculate the total mass of each element in the formula
- Divide each element mass by the total molar mass
- Multiply by 100 to get percentage
Example: Water (H₂O)
Molar mass = 18.015 g/mol
H: (2.016 / 18.015) × 100% = 11.19%
O: (15.999 / 18.015) × 100% = 88.81%
Enter a formula and calculate to see the chart
- Determining empirical formulas from experimental data
- Quality control in chemical manufacturing
- Analyzing mineral composition in geology
- Nutritional analysis of food products
- Environmental pollutant analysis
Enter the chemical formula
Type the compound formula using standard element symbols (like H2O, CO2, or C6H12O6). Numbers after elements indicate atom count.
Click Calculate
The calculator finds atomic masses from the periodic table and computes the total molar mass of your compound.
Review the breakdown
Get instant results showing each element's mass contribution and percentage, plus a visual pie chart distribution.
Accurate atomic masses
Uses standard periodic table values for precise calculations in homework and lab work.
Visual element distribution
Pie chart shows the proportional makeup of your compound at a glance.
Detailed breakdown table
See atomic mass, atom count, total mass, and percentage for each element.
Works with any formula
Handles simple compounds like NaCl and complex molecules like C6H12O6 equally well.
Free and instant
No sign-up required. Results appear immediately in your browser.
How do you calculate percent composition?
Divide the total mass of each element by the compound's molar mass, then multiply by 100. For H2O: hydrogen is (2.016 / 18.015) × 100% = 11.19%.
What is the percent composition formula?
Percent composition = (mass of element in formula / molar mass of compound) × 100%. This gives the mass percentage of each element.
Can this calculator handle complex formulas?
Yes, enter formulas like C6H12O6, Ca(NO3)2, or Fe2(SO4)3. The calculator parses element symbols and their counts automatically.
Why is percent composition important in chemistry?
It helps determine empirical formulas, verify compound purity, and understand the elemental makeup of substances in quality control and research.
What atomic masses does this calculator use?
Standard atomic weights from the periodic table (IUPAC values). For example: H = 1.008, C = 12.01, O = 15.999 g/mol.
Try our other chemistry calculators: the molarity calculator for solution concentrations, the empirical formula calculator to find simplest ratios, and the pH calculator for acid-base calculations.
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