A so-called "end correction" term has long been sought to correlate the experimental result and the theoretical solution for the input admittance of a monopole antenna driven from a coaxial line. The analytic solution of this correction term is possible only in the case of electrically thick monopole. In this communication an integral equal for

, which is related to the integration of the radial

field across the driving point, is formulated for an antenna with arbitrary radius, and subsequently solved by a matrix method. The end correction can then be expressed explicitly in terms of

. The result agrees perfectly with the theoretical solution in the case of an electrically thick monopole.