The tailplane does not produce any lift. You could say it produces a 'Negative Lift'. The reason many early aviators were killed is because the tailplanes produced lift it order to help it fly and the aircraft would then nose up in a tailplane stall, a condition in which it could never recover. Most modern aircraft are designed so that when the airflow decreases, the effect/moment produced by the tail surface is lessened and so the aircraft pitches nose down and therefore safe. This is also the reason why the aircraft will perform more economically with the C of G at its back limit, in this position the load on the tail is the least, whereas at the forward limit the tailplane is producing a high downward load countering the good work done by the mainplanes. This is also the reason why the 'Canard' type of configuration is so good, because the 'canard' will produce lift as well as the mainplanes making it more efficient.
As for the exact pounds/kilos lever-arm produced, it would depend entirely on the aircraft type, the weight to which it was loaded and the C of G.