This **molecular weight calculator** provides you with the molecular weight of any periodic element and the molar mass for any formula you enter in the form.

## What is the molecular weight calculator?

This is a tool that can help you quickly discover the molecular weight of any periodic element or for any formula you enter in the second field.

The *molecular weight calculator* uses the molar mass of each element in the formula you specify to determine the molecular weight of the total compound.

The units used are grams per mole because the molecular weight is usually expressed as the mass of one mole out of a certain substance.

## How to calculate molecular weight of a compound?

In order to calculate the molecular weight of a substance you need to assess the elements and the numbers of atoms from which that substance is composed.

Then you need to discover from the period table of elements the molar masses for those elements. The molar mass is the mass of one atom of an element so this number should be multiplied with the number of atoms in the formula.

Then you need to sum the molar masses corresponding to each element in order to find the molecular weight of the whole substance.

## Let’s take KMn2O4:

There is one atom of K (Potassium) therefore: 39.10 g/mol

There are two atoms of Mn (Manganese) therefore: 2*54.94= 109.88 g/mol

There are four atoms of O (Oxygen) therefore 4*16= 64 g/mol

The molecular weight of a mole of KMn2O4 is (39.10+ 109.88+ 64 = 212.98 g/mol)

09 Apr, 2015