Molecular Weight Calculator
Enter a chemical formula to compute its molar mass and see how much each element contributes. Supports groups like Ca(OH)2, brackets like K4[Fe(CN)6] and hydrates like CuSO4·5H2O.
Enter a chemical formula to calculate its molar mass.
How it works
The molar mass of a compound is the sum of the atomic weights of all the atoms in its formula. The calculator parses the formula, multiplies each element's standard atomic weight by how many times it appears, and adds the contributions together. Parentheses and brackets multiply the group they enclose, and a hydrate written after a middle dot (for example ·5H2O) adds that many water molecules.
The breakdown table shows each element's total mass and its percentage of the whole molecule, which is useful for elemental analysis and for checking a synthesis. Atomic weights are the IUPAC conventional standard values.
Examples
- Water H2O = 18.02 g/mol.
- Glucose C6H12O6 = 180.16 g/mol.
- Copper(II) sulfate pentahydrate CuSO4·5H2O = 249.68 g/mol.
Frequently asked questions
- What is molar mass?
- Molar mass is the mass of one mole of a substance, in grams per mole. It equals the sum of the standard atomic weights of every atom in the chemical formula.
- How do I write a formula?
- Use element symbols with a capital first letter (Na, Cl, Fe), numbers for counts (H2O), parentheses for groups (Ca(OH)2) and a middle dot or period for hydrates (CuSO4·5H2O).
- What is the mass percent column?
- It is each element's share of the total molar mass, calculated as the element's total mass divided by the molar mass. The percentages add up to 100%.
- Is molecular weight the same as molar mass?
- In everyday lab use they are used interchangeably. Strictly, molecular weight is a dimensionless relative mass and molar mass carries units of g/mol, but the numerical value is the same.