GFM Calculator is a simple command-line utility for calculating the gram formula mass (or atomic weight) of a molecular compound.
The individual elements' gram formula mass was pulled from this site.
GFM Calculator requires a molecular compound to be given in algebraic notation.
For example, H2O must be represented as 2*H + O.
Note that the amount of elements must come before the element itself in the * expression. Referencing the example above, H*2 is not permitted, only 2*H.