  Working in the context of the Planck scale cosmology formulation of Bonanno
and Reuter, we use our resummed quantum gravity approach to Einstein's general
theory of relativity to estimate the value of the cosmological constant as
$\rho_\Lambda =(0.0024 eV)^4$. We show that susy GUT models are constrained by
the closeness of this estimate to experiment. We also address various
consistency checks on the calculation. In particular, we use the Heisenberg
uncertainty principle to remove a large part of the remaining uncertainty in
our estimate of $\rho_\Lambda$
