Molecular Weight Calculator

Calculate the molecular weight of chemical compounds from their formulas.

Result

Fill in the fields above, then press Calculate.

A molecular weight calculator computes the molar mass of chemical compounds by summing the atomic weights of each element in the formula.

Enter a chemical formula using standard notation (e.g. H2O, NaCl, C6H12O6, Ca(OH)2). The calculator parses the formula and sums atomic weights from the periodic table to find the molecular weight.

Examples

Water (H2O)

H: 2 x 1.008 = 2.016. O: 1 x 15.999 = 15.999. Total: 18.015 g/mol.

Glucose (C6H12O6)

C: 6 x 12.011 = 72.066. H: 12 x 1.008 = 12.096. O: 6 x 15.999 = 95.994. Total: 180.156 g/mol.

Frequently Asked Questions

What is molecular weight vs molar mass?
Molecular weight (or molecular mass) and molar mass are numerically equal but have different units. Molecular weight is in atomic mass units (amu or Da), while molar mass is in grams per mole (g/mol).
How do I enter formulas with parentheses?
Use standard chemical notation, e.g. Ca(OH)2 for calcium hydroxide. The calculator expands parenthetical groups by the subscript that follows.
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Quick Tips

  • •Capitalize element symbols correctly — Na is sodium, NA would be nitrogen + argon.
  • •For hydrates like CuSO4·5H2O, calculate the anhydrous and water portions separately and add them.