Created By : Rina Nayak

Reviewed By : Rajashekhar Valipishetty

Last Updated : Apr 20, 2023

Atomic Mass Calculator: This atomic mass calculator describes the atomic mass definition and how to get the atomic mass of an atom using the atomic mass formula. It also explains what an atomic mass unit is and why an atom requires neutrons.


Atomic Mass - Definition

The mass of an atom, comprising protons, neutrons, and electrons, is referred to as its atomic mass. However, because each electron is 1,836 times less dense than a proton, electrons make up a small part of the atom's mass in most atoms.

While the atomic mass can be expressed in kilogrammes, it is more common to use atomic mass units (u), also known as daltons, to express it (Da). 1/12 the mass of a carbon-12 atom is one atomic mass unit (one dalton). One atomic mass unit is equal to 1.66 10^-27 kg.

How do you calculate the Mass of an Atom?

We can simply sum the number of protons and neutrons to get a decent approximation of an atom's atomic mass in atomic mass units. As a result, the formula for atomic mass is atomic mass (u) = number of protons + number of neutrons. This formula is quite similar to the formula for the mass number A = Z + N


  • A – Mass number
  • Z – Number of protons
  • N – Number of neutrons

Due to binding energy mass loss, an atom's mass will be somewhat less than its components, which you can determine using E = mc^2. For most atoms, this mass loss is negligible, and our calculator eliminates it.

How can I use the calculator to compute Atomic Mass?

If you're wondering how to calculate atomic mass, our atomic mass calculator is the tool for you. All you have to do is follow the steps below

  • Step 1: Enter the atom's number of protons. If you enter a figure of more than 118, the calculator will warn you because this is the greatest number of protons ever measured in an atom. 
  • Step 2: Enter the atomic number of neutrons. If you enter a value greater than 177, the calculator will warn you because this is the greatest number of neutrons ever recorded in an atom.
  • Step 3: The atomic mass is then displayed in the default unit of atomic mass units by the calculator. By clicking on the unit, you may change the units. 
  • Step 4: In case you need to utilise the atomic mass in a calculation, it also shows the atomic mass in kilogrammes. 
  • Step 5: Finally, it displays the atom's mass number.

Why are neutrons required by Atoms?

You might be wondering why the atom needs neutrons when they have no electric charge. An atom has a neutral charge overall. On the other hand, all of the positive charges is concentrated in the core with the protons. Because like charges repel each other, a force is attempting to tear the nucleus apart.

The attractive strong nuclear attraction that occurs between protons and neutrons opposes this force. As a result, by adding neutrons to the total quantity of attracting strong nuclear force, an atom can prevent itself from breaking up. Some atoms are unstable, and they may only exist for a short time before ejecting some of their constituents and transforming into something different.

FAQs on Atomic Mass Calculator

1. How is an atomic mass calculated?

Every isotope's mass number is the sum of the number of protons and neutrons in its nucleus. Because each proton and neutron have the same atomic mass unit, this is the case (amu). By multiplying the number of protons and neutrons by 1 amu, the mass of an atom can be computed.

2. How is the atomic number calculated?

The number of protons in an element's nucleus determines its atomic number. To put it another way, each element has a distinct number that represents the number of protons in one atom.

3. How many neutrons does hydrogen contain?

A hydrogen atom is made up of one proton, one electron, and no neutrons. The nucleus of a helium atom is made up of two protons and two neutrons, and the helium atom has two electrons.

4. Why don't neutrons exist in hydrogen?

Because the nucleus of hydrogen is so tiny that no heavier neutron can fit inside, it does not contain neutrons. In nature, it also renders hydrogen atoms unstable.