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
'For the sake of persons of ... different types, scientific truth should be presented in different forms, and should be regarded as equally scientific, whether it appears in the robust form and the vivid coloring of a physical illustration, or in the tenuity and paleness of a symbolic expression.'