Enter the number of protons in the isotope and the number of neutrons in the isotope into the Relative Mass Calculator. The calculator will evaluate and display the Relative Mass.

## Relative Mass Formula

The following formula is used to calculate the Relative Mass.

RM = P + N
• Where RM is the Relative Mass (amu)
• P is the number of protons in the isotope
• N is the number of neutrons in the isotope

To calculate the relative mass, sum the number of protons and neutrons in the isotope.

## How to Calculate Relative Mass?

The following example problems outline how to calculate Relative Mass.

Example Problem #1:

1. First, determine the number of protons in the isotope.
• The number of protons in the isotope is given as: 5.
2. Next, determine the number of neutrons in the isotope.
• The number of neutrons in the isotope is provided as: 7.
3. Finally, calculate the Relative Mass using the equation above:

RM = P + N

The values given above are inserted into the equation below and the solution is calculated:

RM = 5 + 7 = 12.00 (amu)

Example Problem #2:

For this problem, the variables needed are provided below:

number of protons in the isotope = 8

number of neutrons in the isotope = 3

This example problem is a test of your knowledge on the subject. Use the calculator above to check your answer.

RM = P + N = ?