Molar Mass Calculator: Calculate Molecular Weight

Calculate the molar mass of any chemical compound.

Chemical Formula

What is Molar Mass?

Molar mass is a physical property defined as the mass of a given substance (chemical element or chemical compound) divided by the amount of substance. The base SI unit for molar mass is kg/mol, but it is almost always expressed in grams per mole (g/mol).

How to Calculate Molar Mass

1
Identify every element in the chemical formula (e.g., in H2O, you have Hydrogen and Oxygen).
2
Find the atomic mass of each element using the Periodic Table (H = 1.008, O = 15.999).
3
Multiply the atomic mass by the number of atoms of that element in the formula.
4
Add the total masses of all elements together to get the final molar mass.

Frequently Asked Questions

What is the difference between Molar Mass and Molecular Weight?

They are often used interchangeably. However, Molecular Weight is technically the mass of a single molecule (measured in amu), while Molar Mass is the mass of one mole of that substance (measured in g/mol).

How do I calculate the molar mass of water (H2O)?

Water has 2 Hydrogens (1.008 × 2 = 2.016) and 1 Oxygen (15.999). Adding them gives: 2.016 + 15.999 = 18.015 g/mol.