The honest answer would be, nobody knows yet. The
current knowledge is that the electron seems to be
a 'point particle' and has refused to show any signs
of internal structure in all measurements. We have
an upper limit on the radius of the electron, set by
experiment, but that's about it. By our current
knowledge, it is an elementary particle with no
internal structure, and thus no 'size'.
Answered by: Yasar Safkan, Ph.D. M.I.T., Software Engineer, Istanbul, Turkey
'Watch the stars, and from them learn. To the Master's honor all must turn, Each in its track, without sound, Forever tracing Newton's ground.'