Molar Mass Calculator

Calculate molar mass (molecular weight) from any chemical formula. Automatically parses formulas with parentheses, brackets, and hydrates. Optionally convert between mass and moles.

Core Formula: Molar Mass = Σ(atomic mass × count for each element) Conversions: Moles = Mass (g) ÷ Molar Mass (g/mol) Mass (g) = Moles × Molar Mass (g/mol) Number of Molecules = Moles × Avogadro's Number Avogadro's Number (Nₐ) = 6.022 × 10²³ Formula Syntax: • Elements: Uppercase + optional lowercase (H, He, Na, Cl) • Numbers: Subscripts after elements (H2O, C6H12O6) • Parentheses: Groups of atoms (Ca(OH)2, Al2(SO4)3) • Hydrates: Use dot or · (CuSO4·5H2O, CaSO4.2H2O) Common Atomic Masses: H=1.008, C=12.01, N=14.01, O=15.999, Na=22.99, Mg=24.31, P=30.97, S=32.06, Cl=35.45, K=39.10, Ca=40.08, Fe=55.85, Cu=63.55, Zn=65.38, Ag=107.87
Example 1 (Water): H₂O = 2×H + 1×O = 2×1.008 + 15.999 = 18.015 g/mol Example 2 (Table Salt): NaCl = 1×Na + 1×Cl = 22.990 + 35.45 = 58.44 g/mol Example 3 (Glucose): C₆H₁₂O₆ = 6×C + 12×H + 6×O = 6×12.01 + 12×1.008 + 6×15.999 = 72.06 + 12.096 + 95.994 = 180.15 g/mol Example 4 (Calcium Hydroxide): Ca(OH)₂ = 1×Ca + 2×O + 2×H = 40.078 + 2×15.999 + 2×1.008 = 74.092 g/mol Example 5 (Copper Sulfate Pentahydrate): CuSO₄·5H₂O = 1×Cu + 1×S + 4×O + 5×(2×H + O) = 63.546 + 32.06 + 4×15.999 + 5×18.015 = 249.686 g/mol Example 6 (Sulfuric Acid): H₂SO₄ = 2×H + 1×S + 4×O = 2×1.008 + 32.06 + 4×15.999 = 98.076 g/mol Mass to Moles Conversion: 36 g H₂O ÷ 18.015 g/mol = 2.00 mol 100 g NaCl ÷ 58.44 g/mol = 1.71 mol

What is molar mass?

Molar mass is the mass of one mole of a substance, expressed in grams per mole (g/mol). It equals the sum of the atomic masses of all atoms in the molecular formula. For example, H₂O has molar mass = 2(1.008) + 15.999 = 18.015 g/mol.

How do I calculate molar mass from a chemical formula?

Count each element in the formula, multiply by its atomic mass from the periodic table, then sum all values. For NaCl: Na (22.99) + Cl (35.45) = 58.44 g/mol. For Ca(OH)₂: Ca (40.08) + 2×O (15.999) + 2×H (1.008) = 74.09 g/mol.

What is the difference between molecular weight and molar mass?

Molecular weight (MW) and molar mass are numerically equal but have different units. Molecular weight is dimensionless (or in amu/Da), while molar mass has units g/mol. In practice, the terms are often used interchangeably in chemistry.

How do I use molar mass in calculations?

Molar mass converts between mass and moles: moles = mass (g) ÷ molar mass (g/mol), and mass (g) = moles × molar mass (g/mol). For example, 44.01 g CO₂ (MM = 44.01 g/mol) equals 1 mole.

Where do I find atomic masses?

Use the periodic table. Common values: H = 1.008, C = 12.01, N = 14.01, O = 16.00, Na = 22.99, Cl = 35.45, Ca = 40.08. Most calculations use rounded values (e.g., H = 1, C = 12, O = 16) for simplicity.

How do I handle hydrates and parentheses?

Multiply the contents of parentheses by the subscript outside. For hydrates, add the water molecules. Example: CuSO₄·5H₂O = Cu (63.55) + S (32.07) + 4×O (16.00) + 5×[2×H (1.008) + O (16.00)] = 249.69 g/mol.

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