The molecular weight calculator computes the molar mass of any chemical compound from its formula. Enter a formula like H2O, NaCl, or C6H12O6 to get molar mass in g/mol with an element-by-element breakdown.
Molecular Weight Calculator
| Element | Count | Atomic Mass | Contribution |
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How to Use the Molecular Weight Calculator
Enter any chemical formula to get its molar mass. The calculator parses element symbols and subscripts, including formulas with parentheses.
Formula Notation
Use standard chemical notation: H2O, NaCl, C6H12O6. For ionic compounds with parenthetical groups: Ca(OH)2, Al2(SO4)3. Element symbols must be properly capitalized: Fe, not FE or fe.
Common Molar Masses
H₂O: 18.015 g/mol. CO₂: 44.009. NaCl: 58.44. Glucose (C₆H₁₂O₆): 180.156. CaCO₃: 100.086. Urea (CH₄N₂O): 60.055. Aspirin (C₉H₈O₄): 180.157.
Using Molar Mass
Moles = mass (g) / molar mass (g/mol). 18 g of water = 1 mol. 100 g of CaCO₃ = 100/100.086 ≈ 0.999 mol ≈ 1 mol.
FAQ
What is molar mass and how is it calculated?
Molar mass is the mass in grams of one mole (6.022 × 10²³ particles) of a substance. It equals the sum of atomic masses of all atoms in the formula. H₂O: 2×1.008 + 15.999 = 18.015 g/mol. CO₂: 12.011 + 2×15.999 = 44.009 g/mol. NaCl: 22.990 + 35.45 = 58.44 g/mol.
What is the difference between molecular weight and formula weight?
Molecular weight applies to molecular compounds (covalent bonds): H₂O, C₆H₁₂O₆, CO₂. Formula weight applies to ionic compounds that don't exist as individual molecules: NaCl, CaCO₃, MgSO₄. Both are calculated the same way (sum of atomic masses) and both are expressed in g/mol.
Is this calculator free?
Yes, completely free with no signup required. All calculations run in your browser.
Is my data private?
Yes. All calculations run locally. Nothing is transmitted.
What formula notation does this accept?
Standard chemical notation: element symbols (H, C, N, O, Na, Fe, etc.) followed by subscript numbers (H2O, C6H12O6). Parentheses for groups: Ca(OH)2 = Ca + 2(O+H) = Ca + 2O + 2H. Nested parentheses not supported for simple formulas.