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Molecular Weight Calculator

An add-in for spreadsheets

Available for both Windows and Mac OSX Excel

ChemicaLogic's Molecular Weight Calculator is an add-in for spreadsheets that you can use to calculate the molecular weight of chemicals. This handy function takes a single string argument which is the chemical formula (or a cell reference containing the chemical formula) and returns the molecular weight.


  • =MW("H2O") returns 18.01528
  • =MW("C2H5OH") returns 46.0694
  • =MW("CaCl2") returns 110.9834

Note that elements are case sensitive. For example, chlorine is "Cl" and not "CL".

See the following example on how to use the Molecular Weight Calculator to calculate the average molecular weight of a mixture and to convert from mole percent to weight percent for a natural gas mixture: Molecular Weight Example (Excel File).

Molecular weight calculator recognizes over 100 atomic species and uses the standard IUPAC atomic weights (2007 Edition) and is available from our online store for:

  • Windows Excel 2016/2013/2010/2007 (32-bit & 64-bit); Only $50
  • Mac OS X Excel 2011; Only $50

If you do not want to purchase our enhanced versions of MWCalc, you can download and use the free version of MWCalc (may have problems in newer versions of Excel and does not work on 64-bit versions of Excel)

MwCalc for Excel 95/97/2000/XP