  We report on a new method to compute the flare reconnection (RC) flux from
post-eruption arcades (PEAs) and the underlying photospheric magnetic fields.
In previous works, the RC flux has been computed using cumulative flare ribbon
area. Here we obtain the RC flux as half of that underlying the PEA associated
with the eruption using an image in EUV taken after the flare maximum. We apply
this method to a set of 21 eruptions that originated near the solar disk center
in Solar Cycle 23. We find that the RC flux from the arcade method ({\Phi}rA)
has excellent agreement with that from the flare-ribbon method ({\Phi}rR)
according to: {\Phi}rA = 1.24({\Phi}rR)^0.99. We also find {\Phi}rA to be
correlated with the poloidal flux ({\Phi}P) of the associated magnetic cloud at
1 AU: {\Phi}P = 1.20({\Phi}rA)^0.85. This relation is nearly identical to that
obtained by Qiu et al. (Astrophys. J. 659, 758, 2007) using a set of only nine
eruptions. Our result supports the idea that flare reconnection results in the
formation of flux rope and PEA as a common process.
