🧪 Molecular Weight Calculator
Enter a chemical formula to get its molecular weight (g/mol) with each element’s contribution, hydrates and nested groups supported.
Molar mass
180.156 g/mol
| Element | Atoms | Atomic wt | Mass | Mass % |
|---|---|---|---|---|
| O Oxygen | 6 | 15.999 | 95.994 | 53.28% |
| C Carbon | 6 | 12.011 | 72.066 | 40.00% |
| H Hydrogen | 12 | 1.008 | 12.096 | 6.71% |
| Total | 180.156 | 100% | ||
IUPAC/CIAAW standard atomic weights. Parser handles nested groups, hydrates (· / . / *) and two-letter symbols. 🔒 Computed in your browser.
How the molecular weight calculator works
The formula is parsed (nested groups, hydrate dots, two-letter symbols) and each element’s count is multiplied by its IUPAC standard atomic weight and summed. The result is the molecular weight in g/mol, with a per-element mass and percent breakdown. For example, sulfuric acid H₂SO₄ sums 2×1.008 + 32.06 + 4×15.999 = 98.08 g/mol. The parse is greedy on two-letter symbols, so it reads “Cl” as chlorine rather than carbon plus something, and multiplies a trailing subscript across the whole preceding parenthesised group.
Molecular weight and molar mass are the same number; this page reports it in g/mol from exact atomic-weight constants, no rounding drift.
Frequently asked questions
How do I find molecular weight from a formula?
Sum the atomic weights of all atoms. Glucose C₆H₁₂O₆ = 6×12.011 + 12×1.008 + 6×15.999 = 180.16 g/mol. The tool parses the formula and computes it exactly.
Is molecular weight the same as molar mass?
Numerically yes. Molecular weight is the relative (dimensionless) mass of a molecule; molar mass is that value in g/mol. This tool shows g/mol.
Can it handle complex formulas?
Yes, nested parentheses/brackets like Ca(NO₃)₂ and K₄[Fe(CN)₆], and hydrates like CuSO₄·5H₂O, are all parsed correctly.
What units are used?
Grams per mole (g/mol), the standard for molar mass / molecular weight.
Is the calculation private?
Yes, everything runs in your browser.
Is molecular weight different from molar mass in practice?
Not numerically, both equal the same summed atomic-weight total. “Molecular weight” is common in biology and older texts; “molar mass” is the SI-consistent term with units of g/mol. This tool reports g/mol.
Does it work for ionic compounds with no molecules?
Yes. Strictly, salts like NaCl form lattices rather than discrete molecules, so the value is a “formula weight”, but it is computed the same way, summing the atomic weights in the formula unit (NaCl = 58.44 g/mol).
How do I find the molecular weight of a hydrate?
Include the waters of crystallisation. For CuSO₄·5H₂O, add the anhydrous CuSO₄ (159.61) to five waters (5 × 18.015 = 90.07), giving 249.68 g/mol. Write the dot as ·, . or * and the tool adds them.
Does molecular weight tell me how heavy one molecule is in grams?
Not directly. It is the mass of one mole (6.022×10²³ molecules) in grams. Divide the molecular weight by Avogadro’s number for one molecule’s mass: water is 18.015 ÷ 6.022×10²³ ≈ 2.99×10⁻²³ g.