Isotope Abundance Calculator

Summary

Enter isotope masses and natural abundances to calculate the weighted average atomic mass of any element.

How it works

1. Add a row for each naturally occurring isotope of the element.
2. Enter the isotope mass (in atomic mass units, u) for each row.
3. Enter the natural abundance (in percent, 0–100) for each row.
4. The calculator multiplies each mass by its fractional abundance and sums the products.
5. The running total of abundances is displayed; it must equal 100% for the result to be valid.
6. Click "Calculate" to see the weighted average atomic mass.

Use cases

• Verify textbook atomic mass values for common elements.
• Practice chemistry homework on isotope mass calculations.
• Explore how isotope ratios affect observed atomic weights.
• Cross-check mass spectrometry data against expected averages.
• Teach or demonstrate the concept of weighted averages in chemistry.
• Calculate average atomic mass for hypothetical or exotic isotope mixtures.

Frequently Asked Questions