The add-in enables you to use chemical formulae in Microsoft Excel. Once entered in a worksheet cell, chemical formulae can be formatted and used in calculations. This add-in provides for the basic chemical calculations like formula weight, percentage composition, reaction coefficients, dilutions and reaction stoichiometry. It also enables you to define and use abbreviations that replace sometimes long formula names or parts of formulae; the abbreviations are afterwards recognized in calculations. Once defined reactions can also be saved.


This add-in also provides a menu to access the functionality, to change the predefined atom weights and to define your own chemical abbreviations. It also provides functions that can be used in spreadsheet cells just like other Excel functions.


The Stoichiometry menu is divided in several groups:

  1. entering molecules and formatting cells which contain chemical formulae. This group also contains a Periodic Table for reference (including all isotopes for each element);

  2. a group of predefined calculations (molecule weight, dilution of a given solution, percentage composition of a given chemical). These calculations are made in a pop-up box where the data are typed in and the result of the calculation appears in the box;

  3. a group relating to chemical reactions: calculation of the coefficients of a given chemical reaction and making/using your list of stored reactions; 

  4. a utility to extract all the composing atoms of a chemical and to copy the symbols in a range in the spreadsheet; a utility to draw (organic) molecules from their SMILES notation (the free OpenBabel software needs to be installed on your computer- see manual); 

  5. a group of functions that enable you to work with your own chemical abbreviations;

  6. settings for this add-in, and some informative screens (short help function).


For the calculation of molecular weights, the add-in recognises 118 atoms (average atomic weight) and 3178 isotopes. These weights are also used in the calculation of compositions and reactions and allows as such calculations based on the isotopes instead of average atomic weights.

Also a database with over 60000 molecules is attached to help you find the chemical formula of a named chemical.


The stoichiometry functions can be used in spreadsheet cells just like other Excel functions. The functions calculate:

  1. the molecular weight of a given molecule;
  2. the weight fraction of a given structure in a molecule;
  3. the reaction coefficient of a reagent or product in a chemical reaction defined by a range of reactants and a range of products;
  4. the number of a given atom in a given molecule;
  5. the atom number of a given atom;
  6. the weight of a reagent or product in a chemical reaction defined by a range of reactants and a range of products, when an amount of one of the products or reactants is given.
  7. the monoisotopic mass and the nominal weight of molecules (specifically used in mass spectroscopy).

Some functions can return general data on each of the elements, like their group or period, ionisation energy, or electron configuration.

Also, a function is provided to extract the atoms from one or more molecules.


A manual is available in the download section.


The add-in works with Microsoft Excel 2007 / 2010 / 2013 / 2016 under Windows Vista / 7 / 8 / 10.

It does not work with other operating systems or older versions of Excel.