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Atomic Mass Calculator

Atomic Mass Calculator is an online tool that provides the atomic mass of an atom by taking 2 parameters. Simply enter the inputs i.e number of protons, number of neutrons in the input fields of the calculator and then click on the calculate button to avail the output.

Number of Protons (Z)
Number of Neutrons (N)

Atomic Mass Calculator: Are you trying to learn about the atomic mass concept? If so, you have arrived the right way as our free tool finds the atom atomic number and saves your energy, time. We will explain all the details about the atomic mass such as definition, steps to solve it, formula and so on. Also, get the example uestions with answers in the later sections of this page.

How to Find Atomic Mass?

Below given is the step by step process to calculate the atomic mass. Follow these rules and regulations to check the answer easily.

  • Know the number of protons, number of neutrons of an atom.
  • Add number of protons to the number of neutrons.
  • The sum is the atomic number.

Atomic Mass Defintion & Formula

The atomic mass is defined as the mass of an atom including its protons, neutrons and electrons. Anyway, the electron is 1836 times lesser than the mass of the proton, the electron is neglectable in most of the atoms. The atomic mass unit is Dalton that is represented as Da. The atomic mass is different for different elements. It depends on the number of neutrons, protons of an element.

The atomic mass formula is along the lines:

Atomic mass (A) = Number of Protons + Number of Neutrons

A = Z + N

Mass Number = Z + N


A is the atomic mass

Z is the number of protons

N is the number of neutrons


Question: What is the atomic mass of the given chlorine sample where isotopes are mixed. The first isotope has an atomic mass of 34.5 nad abundance of 75%. The second isotope has an atomic mass of 36.9 and abundance of 24.2%.


Atomic mass of each isotope x (Abundance%/100) = 34.5 x 0.75 = 25.875

= 36.9 x 0.242 = 8.929

Atomic mass of the sample = 8.929 + 25.875 = 34.80

Therefore, the atomic mass of the given sample of chlorine is 34.80 u

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FAQ’s on Atomic Mass Calculator

1. How to find atomic mass without a calculator?

The simple trick to calculate the atomic mass of an atom is just to add the number of protons and neutrons in it.

2. What is the formula for relative atomic mass?

The average mass of an element is called the relative atomic mass. The relative atomic mass = number of protons + number of neutrons.

3. What is meant by atomic mass?

Atomic mass is the mass of the atom of a chemical element. It is the sum of three subatomic particles like protons, neutrons and electrons. It is used to calculate the average mass of the molecules and elements.

4. What is the difference between atomic mass and atomic weight?

Atomic mass is the sum of neutrons and protons present in an atom while atomic weight is the average of the ratio of atoms present in the element. Atomic weight is the analysis done by mass spectroscopy and atomic mass is the analysis done by mass spectroscopy.