Molar Mass Calculator
Calculate the total molar mass of a molecule and view the percentage of each atom and mass contribution. Ideal for chemistry students and professionals.
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.