分子量計算機

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.

完全なユーザーガイド

分子量とは何ですか?

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.

式

分子量: MW = Σ (Atomic Weight × Count)

Mass %: % = (Element Mass / MW) × 100

Supported Formula Formats

Simple Formulas

H2O、CO2、NaCl、Fe2O3 — 単なる要素と添え字。

Parentheses

Ca(OH)2、Al2(SO4)3 — 乗数を持つグループ。

Hydrates

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

Complex Compounds

C8H10N4O2（カフェイン）、C9H8O4（アスピリン）など

Common Molecular Weights

• H₂O (水) = 18.015 g/mol

• CO₂ (二酸化炭素) = 44.009 g/mol

• NaCl (食塩) = 58.443 g/mol

• C₆H₁₂O₆ (グルコース) = 180.156 g/mol

• Ca(OH)₂ (水酸化カルシウム) = 74.093 g/mol

• C₈H₁₀N₄O₂ (カフェイン) = 194.190 g/mol

• C₂H₅OH (エタノール) = 46.069 g/mol

重要な注意事項

  • Element symbols are case-sensitive: Na (sodium) vs NA (invalid).
  • Parentheses must be properly balanced.
  • 原子量はIUPAC規格値です。
  • Mass percentages always sum to 100%.

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