Possibly by puting it inside a span and testing the size of the span.
Of course you also need to allow for when the letter doesn't have a font or size such as when it has a voice and pitch instead. You also can't rely on what you put in your stylesheet since your visitors can easily change it to suit themselves.
Thanks for the reply. I was actually wondering if there was a way to do it on the fly. If some one at some time did some sort of averaging of letter widths. I do at this point calculate the height of the lement based upon the font size but the width is eluding me.