Calculate molecular weight

Sum atomic weights from a chemical formula, including parenthesized groups.

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ToolMolecular Weight Calculator
Input
Output
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How it works

A formula is parsed into element symbols and counts, each count is multiplied by stored atomic weight, and the products are summed. Parentheses multiply the enclosed group before summation.

  • Standard atomic weights describe ordinary composition.
  • Isotopic enrichment is not inferred.

Worked example

Slaked lime
Ca(OH)2 with brackets around the hydroxide group
Input
											Ca(OH)2
Output
												Molar mass: 74.092
Formula: Ca(OH)2
Element count: 3
Atom count: 5

When to use this

Reagent labels check molar mass, stoichiometry converts grams to moles, and mass spectrometry compares formula mass with an ion.

Edge cases

  • Ca(OH)2 counts oxygen and hydrogen twice.
  • Malformed element-symbol casing is rejected.
  • Isotope-labelled compounds need isotope-specific masses.

References