This average atomic mass calculator determines the weighted average of a chemical element, by factoring in isotopic masses and their natural abundance in a sample. For each isotope, specify the mass and the percentage abundance in a given element.
“Average atomic mass is the weighted average of the masses of all naturally occurring isotopes of an element”
Average atomic mass is also known as average atomic weight. The mass of one mole of an atom of an element is equal to the average atomic mass of that element in grams.
This average atomic mass calculator helps you to find the mass of a mole of an atom for a given element.
Average atomic mass is expressed in kg; generally, it is expressed in a non-SI unit known as amu. This unit is used for comparing the masses of various atoms and molecules.
Our average atomic mass calculator operates well by considering some values with their respective abundance. By using these inputs, our tool performs vital calculations in just a click.
Input:
Output:
The formula for calculating the average atomic mass (A) is:
AM = ( Mass of Isotope1 × Abundance1 ) + ( Mass of Isotope2 × Abundance2 ) + …
In the given formula, each term represents the mass of an isotope multiplied by its abundance, and the sum is taken over all isotopes of the element.
By looking up the natural abundance and the mass of their isotopes, our average atomic mass calculator calculates fast results in a fraction of a second.
Chlorine Isotopes: -35 and -37
The average atomic mass of chlorine is calculated as follows:
= (34.969 amu * 0.7577) + (37.9627 amu * 0.2423)
= 35.45 amu
Suppose, an element has three isotopes hydrogen, deuterium, and tritium. So, find their average atomic mass?
When expressing natural abundance (f) values as a percentage, divide by 100.
AM = ( Abundance1 x Mass ) + ( Abundance2 x Mass ) + … / 100
AM = [ (99.9885 x 1.007825) + (0.0115 x 2.014101) + (11 x 3.01605) ] / 100
AM = 1.33970622174
If two or more forms of the same element have the same number of protons but different numbers of neutrons in their nuclei is known as anisotope.
AMU is the short form of atomic mass unit. “It is defined as 1/12 of the mass of an unbound atom of carbon-12”.
One amu = 1.66053907015 × 10⁻²⁷ kilograms
This is a very small mass, but it is convenient for comparing the masses of atoms and molecules. This can help you in calculating average atomic mass.
The sum of protons and the neutrons of an atom is known as the mass number. it is denoted by A
ELEMENT | ATOMIC NUMBER | ATOMIC MASS |
Hydrogen | 1 | 1.008 |
Helium | 2 | 4.0026 |
Lithium | 3 | 6.94 |
Beryllium | 4 | 9.0122 |
Boron | 5 | 10.81 |
Carbon | 6 | 12.011 |
Nitrogen | 7 | 14.007 |
Oxygen | 8 | 15.999 |
Fluorine | 9 | 18.998 |
Neon | 10 | 20.180 |
Sodium | 11 | 22.990 |
Magnesium | 12 | 24.305 |
Aluminium | 13 | 26.982 |
Silicon | 14 | 28.085 |
Phosphorus | 15 | 30.974 |
Sulfur | 16 | 32.06 |
Chlorine | 17 | 35.45 |
Argon | 18 | 39.948 |
Potassium | 19 | 39.098 |
Calcium | 20 | 40.078 |
Scandium | 21 | 44.956 |
Titanium | 22 | 47.867 |
Vanadium | 23 | 50.942 |
Chromium | 24 | 51.996 |
Manganese | 25 | 54.938 |
Iron | 26 | 55.845 |
Cobalt | 27 | 58.933 |
Nickel | 28 | 58.693 |
Copper | 29 | 63.546 |
Zinc | 30 | 65.38 |
Bio.libretexts: Average Atomic Mass, Isotopes, Calculating Average Atomic Mass
Wikipedia: Atomic mass, Relative isotopic mass, Similar terms for different quantities, Mass defect, Measurement of atomic masses, Relationship between atomic and molecular masses.
Chem.libretexts: Calculating Average Atomic Mass, Have you ever tried to move a boulder? Percent Natural Abundance, Example.
Keep in touch
Contact Us© Copyright 2025 by calculatored.com