Molecular Weight Calculator
Calculate molar mass for any chemical formula using IUPAC standard atomic weights
Note: Formula is case-sensitive (e.g. C for carbon, Ca for calcium)
Water (H₂O)
Glucose (C₆H₁₂O₆)
Salt (NaCl)
Sulfuric Acid (H₂SO₄)
Ethanol (C₂H₅OH)
Calculation Result
18.015 g/mol
Molecular weight for H₂O
Elemental Composition
| Element | Atoms | Atomic Mass | Contribution |
|---|---|---|---|
| Hydrogen (H) | 2 | 1.008 g/mol | 2.016 g/mol |
| Oxygen (O) | 1 | 15.999 g/mol | 15.999 g/mol |
Understanding Molecular Weight
Molecular Weight Definition
Molecular weight (also called molecular mass or molar mass) is the sum of the atomic weights of all atoms in a molecule. It is expressed in atomic mass units (u) or grams per mole (g/mol).
In chemistry, molecular weight is used to:
- Calculate concentrations for solutions
- Determine stoichiometry in chemical reactions
- Convert between mass and moles of a substance
- Calculate empirical formulas from elemental analysis
Calculation Notes
This calculator uses the abridged standard atomic weights published by IUPAC (International Union of Pure and Applied Chemistry).
Important considerations:
- Formulas are case-sensitive (C = carbon, Ca = calcium)
- Use parentheses for groups: Al₂(SO₄)₃
- Isotopes are not distinguished (average atomic mass is used)
- Hydrates can be entered with dot notation: CuSO₄·5H₂O
- Uncertainty in atomic weights is ignored for simplicity
The terms “molecular weight” and “molar mass” are used interchangeably in chemistry.
Frequently Calculated Compounds
| Compound | Formula | Molecular Weight (g/mol) |
|---|---|---|
| Water | H₂O | 18.015 |
| Table Salt | NaCl | 58.443 |
| Sucrose | C₁₂H₂₂O₁₁ | 342.297 |
| Ethanol | C₂H₅OH | 46.069 |
| Carbon Dioxide | CO₂ | 44.010 |
| Sulfuric Acid | H₂SO₄ | 98.079 |