Atomic Mass Calculator
Result
Atomic Mass Calculator Calculate the average atomic mass of an element from the masses and natural abundances of two isotopes. The calculator takes the abundance-weighted mean: (m₁·a₁ + m₂·a₂) ÷ (a₁ + a₂). Enter each isotope's mass in atomic mass units (u — free online calculator.
Formula
- Atomic Mass Calculator calculates its result from A1, A2, M1, M2. It uses the formula Atomic mass = (m1 x a1 + m2 x a2) / (a1 + a2). Change any input to recalculate the result instantly.
- The main inputs are A1, A2, M1, M2. Enter them in the units and format shown in the calculator.
- Use the units, labels and assumptions shown beside each input so the formula is applied consistently.
- Changing any input above recalculates the result with the same calculation engine used by this page.
Example: Atomic Mass
- A1: 2
- A2: 3
- M1: 4
- M2: 5
Using A1 = 2, A2 = 3, M1 = 4, M2 = 5, the calculated result is 4.6.
Sample result: Calculating…
Frequently asked questions
What does the Atomic Mass calculate?
Atomic Mass Calculator Calculate the average atomic mass of an element from the masses and natural abundances of two isotopes. The calculator takes the abundance-weighted mean: (m₁·a₁ + m₂·a₂) ÷ (a₁ + a₂). Enter each isotope's mass in atomic mass units (u — free online calculator.
Which values should I enter?
Enter A1, A2, M1, M2 using the units and format shown beside each field.
What formula does this calculator use?
The calculator uses the following relationship: Atomic mass = (m1 x a1 + m2 x a2) / (a1 + a2).
Why might my result differ from another source?
Results can differ when another source uses different units, rounding rules, conventions or assumptions. Compare the inputs and definitions before comparing results.
Does the result update automatically?
Yes. Changing an input updates the result using the same calculation engine shown on this page.