http://stackoverflow.com/questions/349705/total-width-of-element-including-padding-and-border-in-jquery
The original answer was written prior to jQuery 1.3, and the functions that existed at the time where not adequate by themselves to calculate the whole width.
Now, as J-P correctly states, jQuery has the functions outerWidth and outerHeight which include the border
and padding
by default, and also the margin
if the first argument of the function is true