  The main aim of this paper is essentially to point out that the Buchdahl
compactness limit of a static object is given by \it{gravitational field energy
being less than or equal to half of its non-gravitational matter energy}. It is
thus entirely determined without any reference to interior distribution by the
exterior unique solutions, the Schwarzschild for neutral and the
Reissner-Nordstr{$\ddot o$}m for charged object. In terms of surface potential,
it reads as $\Phi(R) = (M-Q^2/2R)/R \leq 4/9$ which translates to surface
red-shift being less than or equal to $3$. It also prescribes an upper bound on
charge an object could have, $Q^2/M^2 \leq 9/8 > 1$.
