Atomic Mass Calculator

Find mass number from protons and neutrons.

Mass number 12

Formula: mass number = protons + neutrons

Step-by-step with your numbers:

1. Values used:

2. Protons = 6

3. Neutrons = 6

5. Mass number = Protons + Neutrons = 6 + 6 = 12

Did we solve your problem today?

The mass number is the total count of protons and neutrons (nucleons).

The math behind it

mass number (A) = protons + neutrons. Electrons are too light to count.

Carbon-12: 6 + 6 → 12.

Atomic mass vs mass number?

Mass number is a whole count; atomic mass (amu) is slightly different due to binding energy.