Molar Mass Calculator
Calculate the molar mass (molecular weight) of any chemical compound from its formula. Enter a chemical formula like H2O, NaCl, or C6H12O6 and this calculator computes the molar mass in grams per mole (g/mol) by summing the atomic masses of all atoms in the molecule. Essential for stoichiometry, molarity calculations, and converting between grams and moles in chemistry.
Use element symbols with subscript numbers (e.g., H2O, NaCl, C6H12O6, H2SO4)
How to Calculate Molar Mass
- Identify each element in the chemical formula
- Count the number of atoms of each element (subscript numbers)
- Look up the atomic mass of each element from the periodic table
- Multiply each atomic mass by the number of atoms
- Sum all the subtotals to get the molar mass
Formula:
M = Σ (number of atoms × atomic mass of element)
Example: H₂O = 2(1.008) + 1(15.999) = 18.015 g/mol
Common Compound Molar Masses
| Compound | Formula | Molar Mass (g/mol) |
|---|---|---|
| Water | H2O | 18.015 |
| Sodium Chloride (Salt) | NaCl | 58.440 |
| Carbon Dioxide | CO2 | 44.009 |
| Glucose | C6H12O6 | 180.156 |
| Sulfuric Acid | H2SO4 | 98.079 |
| Sodium Hydroxide | NaOH | 39.997 |
| Hydrochloric Acid | HCl | 36.461 |
| Calcium Carbonate | CaCO3 | 100.087 |
| Ammonia | NH3 | 17.031 |
| Ethanol | C2H5OH | 46.069 |
Frequently Asked Questions
What is molar mass?
Molar mass is the mass of one mole (6.022 × 10²³ particles) of a substance, expressed in grams per mole (g/mol). It numerically equals the molecular weight or formula weight of the compound.
What is the molar mass of water (H₂O)?
The molar mass of water is 18.015 g/mol. This is calculated as: 2 hydrogen atoms (2 × 1.008 = 2.016) + 1 oxygen atom (15.999) = 18.015 g/mol.
What is the difference between molar mass and molecular weight?
They are numerically the same but technically different. Molar mass has units of g/mol and refers to one mole of substance. Molecular weight (or relative molecular mass) is dimensionless and refers to a single molecule relative to 1/12 of carbon-12.
How do I convert grams to moles using molar mass?
Divide the mass in grams by the molar mass: moles = grams ÷ molar mass (g/mol). For example, 36 grams of water: 36 ÷ 18.015 = 2.0 moles of H₂O.
Where do atomic masses come from?
Atomic masses are determined experimentally using mass spectrometry and are published by IUPAC (International Union of Pure and Applied Chemistry). They represent weighted averages of all naturally occurring isotopes of each element.