Molar Mass Calculator
Enter any chemical formula and get the molecular weight with a step-by-step element breakdown.
How It Works
The molar mass of a compound is the sum of the atomic masses of every atom in the formula, measured in grams per mole (g/mol). It tells you the mass of one mole — 6.022 × 10²³ particles — of that substance.
To calculate it, first parse the chemical formula to identify each element and how many atoms of it appear. Parenthesized groups like (OH)₂ multiply every atom inside by the subscript. Hydrates like CuSO₄·5H₂O add the water molecules separately.
Then multiply each element's count by its standard atomic weight (from IUPAC 2021 data) and sum the results. This calculator uses the same atomic masses as your textbook and shows every step so you can follow the math.
Because molar mass is a sum, the significant figures rule for addition applies: the result is rounded to the same number of decimal places as the least precise atomic mass in the formula. For example, if sulfur's mass is known to two decimal places (32.06), the total is rounded to two decimal places — no matter how precisely the other masses are known.
Molar mass is essential for stoichiometry — converting between grams and moles in balanced chemical equations, preparing solutions of known concentration, and calculating yields in lab experiments.