The molecular mass (Mr) or molecular weight MW of a substance, is the mass of one molecule of that substance, relative to the unified atomic mass unit u (equal to 1/12 the mass of one atom of ¹²C, see also relative atom masses). Due to this relativity, the molecular mass of a substance is commonly referred to as the relative molecular mass (abbreviated to Mr). Note that the molecular mass depends on the isotopic composition of the particular molecule. This program uses the natural abundances of all stable isotopes of a particular element to calculate the "chemical" molecular weight.

Download
English version	[726 kB]
After downloading please unpack all files of the zipped packages and start the executable.

The program MolWeight calculates the average molecular weight of a compound. The molecular formula of this compound can be entered by selecting the appropriate elements and their multipliers. The average atomic weight of an element is displayed if the user moves the mouse over a particular element symbol.
Many thanks to Ihor Patsay, Ivan Franko National University of L’viv, Ukraine, who contributed the molecular weight calculator to the Learning by Simulations Web site.