Molar Mass Calculator
Enter a neutral chemical formula and get its molar mass with a step-by-step element breakdown.
Learning about moles? Read the Moles & Composition study guide →
Common Molar Masses
Molar masses of everyday compounds, computed with the same method and atomic weights as the calculator above. Select any formula to load it and see the full breakdown.
| Compound | Formula | Molar Mass |
|---|---|---|
| Water | 18.015 g/mol | |
| Table salt (sodium chloride) | 58.44 g/mol | |
| Carbon dioxide | 44.009 g/mol | |
| Glucose | 180.156 g/mol | |
| Sulfuric acid | 98.07 g/mol | |
| Sodium hydroxide (lye) | 40.00 g/mol | |
| Hydrochloric acid | 36.46 g/mol | |
| Ammonia | 17.031 g/mol | |
| Calcium carbonate | 100.086 g/mol | |
| Sodium bicarbonate (baking soda) | 84.01 g/mol | |
| Ethanol | 46.069 g/mol | |
| Acetic acid | 60.052 g/mol | |
| Methane | 16.043 g/mol | |
| Oxygen gas | 31.998 g/mol | |
| Nitrogen gas | 28.014 g/mol | |
| Calcium hydroxide | 74.092 g/mol | |
| Potassium permanganate | 158.032 g/mol | |
| Copper(II) sulfate | 159.60 g/mol | |
| Iron(III) oxide | 159.687 g/mol |
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 (approximately 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 and sum the results. The calculator uses ChemWhiz's periodic-table values, based on the IUPAC periodic table released in 2022, and shows every step.
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.
The parser supports neutral formulas, nested parentheses or brackets, and hydrates. Enter one formula unit without a leading reaction coefficient. Charged ions, isotope notation, and variable-composition materials are outside this calculator's input grammar.
Atomic-weight reference: IUPAC Periodic Table of the Elements.
Frequently Asked Questions
What is molar mass?
Molar mass is the mass of one mole (approximately 6.022 × 10²³ particles) of a substance, measured in grams per mole (g/mol). For a compound it equals the sum of the standard atomic masses of every atom in its chemical formula.
How do you calculate molar mass?
Multiply the number of each type of atom in the formula by that element’s standard atomic mass, then add the results. For water (H₂O): 2 × 1.008 (hydrogen) + 1 × 15.999 (oxygen) = 18.015 g/mol.
What is the difference between molar mass and molecular weight?
Numerically they are the same for a given substance. Molar mass carries the unit g/mol and refers to one mole, while molecular weight (relative molecular mass) is a dimensionless ratio. In everyday chemistry the terms are used interchangeably.
What is the molar mass of water?
The molar mass of water (H₂O) is 18.015 g/mol: two hydrogen atoms (2 × 1.008) plus one oxygen atom (15.999).
What units is molar mass measured in?
Grams per mole (g/mol). Because one mole is approximately 6.022 × 10²³ formula units, the molar mass tells you how many grams make up that many units of the substance.