Calculateur de poids moléculaire

Calculate molecular weight (molar mass) from any chemical formula. Supports parentheses, hydrates, and complex compounds. Free, fast, and easy to use.

Enter Formula

Use proper capitalization: H2O (not h2o). Use · or * for hydrates.

Enter a chemical formula (e.g. H2O, C6H12O6, Ca(OH)2) and click Calculate to get the molecular weight, element breakdown, and step-by-step solution.

Guide d'utilisation complet

Qu’est-ce que le poids moléculaire ?

Molecular weight (also called molar mass) is the total mass of one mole of a compound, calculated by summing the atomic weights of every atom in its chemical formula. It is expressed in grams per mole (g/mol) and is fundamental to converting between mass and moles in stoichiometry, solution preparation, and analytical chemistry.

Formule

Poids moléculaire: MW = Σ (Atomic Weight × Count)

Mass %: % = (Element Mass / MW) × 100

Supported Formula Formats

Simple Formulas

H2O, CO2, NaCl, Fe2O3 — juste des éléments et des indices.

Parentheses

Ca(OH)2, Al2(SO4)3 — groupes avec multiplicateurs.

Hydrates

CuSO4·5H2O — use · or * for dot notation.

Complex Compounds

C8H10N4O2 (caféine), C9H8O4 (aspirine), etc.

Common Molecular Weights

• H₂O (Eau) = 18,015 g/mol

• CO₂ (Dioxyde de Carbone) = 44,009 g/mol

• NaCl (sel de table) = 58,443 g/mol

• C₆H₁₂O₆ (Glucose) = 180,156 g/mol

• Ca(OH)₂ (hydroxyde de calcium) = 74,093 g/mol

• C₈H₁₀N₄O₂ (Caféine) = 194,190 g/mol

• C₂H₅OH (éthanol) = 46,069 g/mol

Remarques importantes

  • Element symbols are case-sensitive: Na (sodium) vs NA (invalid).
  • Parentheses must be properly balanced.
  • Les poids atomiques sont des valeurs standard IUPAC.
  • Mass percentages always sum to 100%.

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