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The molar mass calculator quickly determines the molar mass and  the percentage mass composition of a substance bases upon it's chemical formula. It uses the relative atomic weights of the elements. The calculator is found on the right hand side panel of this page.


What is Molar mass?

A mole is a quantity that chemists use in calculations involving mass, volume, concentration and number of particles. One mole has been defined as the number of atoms in excactly 12 grams of Carbon-12. This number very large and is approximately 6.022 x 1023

The molar mass of a chemical species is defined as the number of grams that one mole of a chemical weighs. The units for molar mass are g mol-1 or grams per mole.

The molar mass is calculated by adding up the relative atomic weights of each element in a chemical species according to the chemical formula of that species. The term 'formula mass' is often used instead of molar mass.


Molar mass calculations


Ar = relative atomic weight of an element.

The relative atomic weights of the elements can be found on a Periodic Table

M = molar mass of a chemical species in g mol-1 or g/mol


Calculate the molar mass of the following chemical substances.


1. Water, H2O

M(H2O) = 2 x Ar(H) + 1 x Ar(O)

M(H2O) = 2 x 1.00794 + 1 x 15.9994

                = 18.0153 g mol-1


2.  Oxygen, O2

M(O2) = 2 x Ar(O)

M(O2) = 2  x 15.9994

                = 31.9988 g mol-1


3. Sodium chloride, NaCl

M(NaCl) = 1x Ar(Na) + 1 x Ar(Cl)

M(NaCl) = 1  x 22.98976928 + 1 x 35.453

                = 58.4428 g mol-1


4. Glucose, C6H12O6

M(C6H12O6) = 6 x Ar(C) + 12 x Ar(H) + 6 x Ar(O)

M(C6H12O6) = 6 x 12.0107 + 12 x 1.00794 + 6 x 15.9994

M(C6H12O6) = 180.1559 g/mol


5. Sulfuric acid, H2SO4

M(H2SO4) = 2 x Ar(H) + 1 x Ar(S) + 4 x Ar(O)

M(H2SO4)) = 2 x 1.00794 + 1 x 32.065 + 4 x 15.9994

M(H2SO4)) = 98.0785 g/mol


Molar mass calculator - Instructions

Enter the chemical formula into the molar calculator and press calculate.

The molar mass is quickly calculated.

Please modify chemical formulas that include water of crystallization to avoid errors.

For example copper sulfate, CuSO4.5H2O is changed to CuSO4(H2O)5

The calculator produces a molar mass of 249.6850 g/mol