Molar Mass Calculator

How to Use the Molar Mass Calculator

The Molar Mass Calculator determines the molecular weight of any chemical compound from its formula. Enter a chemical formula like H2O, NaCl, or C6H12O6, and the calculator breaks down the atomic masses of each element and sums them to give the total molar mass in grams per mole.

How to Enter Formulas

Type the chemical formula using standard notation. Element symbols are case-sensitive (Co is cobalt, CO is carbon monoxide). Use numbers for subscripts: H2O, NaCl, C6H12O6, Ca(OH)2. Parentheses indicate groups: Ca(OH)2 means one calcium, two oxygens, and two hydrogens.

Calculation Method

The calculator looks up the atomic mass of each element from the periodic table and multiplies by the number of atoms of that element in the formula. For H2O: H = 1.008 × 2 = 2.016, O = 15.999 × 1 = 15.999. Total molar mass = 18.015 g/mol.

Common Molar Masses

Water (H₂O): 18.015 g/mol. Carbon dioxide (CO₂): 44.009 g/mol. Glucose (C₆H₁₂O₆): 180.156 g/mol. Sodium chloride (NaCl): 58.443 g/mol. Ethanol (C₂H₅OH): 46.069 g/mol. Aspirin (C₉H₈O₄): 180.157 g/mol. Caffeine (C₈H₁₀N₄O₂): 194.190 g/mol.

Element Composition

The calculator shows the mass percentage of each element. In water: hydrogen is 11.19% and oxygen is 88.81%. In glucose: carbon is 40.00%, hydrogen is 6.71%, and oxygen is 53.29%. This composition analysis is useful for stoichiometry and nutritional chemistry.

Applications in Chemistry

Molar mass is essential for converting between grams and moles in stoichiometric calculations. To find how many moles are in 36 grams of water: 36 / 18.015 = 2.0 moles. To find the mass of 0.5 moles of NaCl: 0.5 × 58.443 = 29.22 grams. Every quantitative chemistry calculation requires molar mass.

Frequently Asked Questions

Q: What is the difference between molecular weight and molar mass?

A: Molar mass (g/mol) is the mass of one mole (6.022 × 10²³) of molecules. Molecular weight (or relative molecular mass) is a dimensionless ratio of the molecule mass to 1/12 the mass of carbon-12. Numerically, they are the same. Molar mass has units (g/mol); molecular weight does not.

Q: How do I handle hydrated compounds?

A: Enter the full formula including water of crystallization. CuSO4·5H2O (copper sulfate pentahydrate) can be entered as CuSO4(H2O)5 or CuS O4H10O5. The molar mass is 249.685 g/mol, including the five water molecules.

Q: Why do atomic masses have decimal values?

A: Atomic masses reflect the natural isotope mixture of each element. Carbon has a mass of 12.011 because natural carbon is 98.9% carbon-12 (mass 12) and 1.1% carbon-13 (mass 13.003). The weighted average of all stable isotopes gives the standard atomic mass used in calculations.