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Free chemistry tool: Calculate molecular weight, molar mass & mass percentage from chemical formulas. Includes periodic table, element builder & common compounds database. Perfect for students & chemists!
Choose your input method
Enter chemical formula using element symbols (e.g., H2O, C6H12O6)
Use capital letters for element symbols (H, C, O, Na, Cl)
Numbers after elements indicate quantity (H2O = 2 hydrogen, 1 oxygen)
Use Element Builder to construct formulas visually
Accurate atomic weights from periodic table
Mass percentage calculation for each element
Quick access to common compounds
Visual element builder with periodic table
Calculation history for quick reference
Molecular weight (MW), also called molecular mass or molar mass, is the sum of the atomic weights of all atoms in a molecule. It's expressed in atomic mass units (amu) or grams per mole (g/mol). Molecular weight is fundamental to chemistry calculations, stoichiometry, and understanding chemical reactions. This calculator uses standard atomic weights from the International Union of Pure and Applied Chemistry (IUPAC) periodic table for accurate results.
Key Characteristics:
| Compound Name | Formula | Molecular Weight | Category |
|---|---|---|---|
| Water | H₂O | 18.015 g/mol | Common |
| Glucose | C₆H₁₂O₆ | 180.156 g/mol | Organic |
| Sodium Chloride | NaCl | 58.44 g/mol | Inorganic |
| Sulfuric Acid | H₂SO₄ | 98.079 g/mol | Acid |
| Carbon Dioxide | CO₂ | 44.01 g/mol | Common |
| Ammonia | NH₃ | 17.031 g/mol | Common |
| Ethanol | C₂H₅OH | 46.069 g/mol | Organic |
| Calcium Carbonate | CaCO₃ | 100.087 g/mol | Inorganic |
Molecular weight (MW) is the sum of atomic weights of all atoms in a molecule, expressed in g/mol or amu. Formula: MW = Σ(atomic weight × number of atoms). Example: H₂O = (2×1.008) + (1×15.999) = 18.015 g/mol.
Steps: 1) Identify each element and count atoms. 2) Find atomic weight from periodic table. 3) Multiply atomic weight by atom count. 4) Sum all values. Example: NaCl = Na(22.99) + Cl(35.45) = 58.44 g/mol.
Molecular weight and molar mass are numerically identical but differ in concept. Molecular weight is the mass of one molecule measured in atomic mass units (amu), while molar mass is the mass of one mole of substance measured in grams per mole (g/mol). In practice, both terms are often used interchangeably in chemistry.
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