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Atomic Mass Calculator

Weighted average atomic mass from two isotopes.

Compute the weighted-average atomic mass of an element with two stable isotopes from each isotope's mass and natural abundance.

Daniel Oh By Daniel Oh
Reviewed by Dr. Helena Ortiz
Published Last reviewed 1 min read

Inputs

u
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u
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Results

Enter values and click Calculate to see results.
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How to use this calculator

  1. Fill in the inputs above using the units you already have.
  2. Values update automatically as you type — no submit button needed.
  3. Hover any result row for the underlying formula and intermediate values.

Formula

M̄ = m₁·f₁ + m₂·f₂ with f₁ + f₂ = 1.

In depth

Compute the weighted-average atomic mass of an element with two stable isotopes from each isotope's mass and natural abundance.