  The $E = 0$ octet of bilayer graphene in the filling factor range of -4 <
$\nu$ < 4 is a fertile playground for many-body phenomena, yet a Landau level
diagram is missing due to strong interactions and competing quantum degrees of
freedom. We combine measurements and modeling to construct an empirical and
quantitative spectrum. The single-particle-like diagram incorporates
interaction effects effectively and provides a unified framework to understand
the occupation sequence, gap energies and phase transitions observed in the
octet. It serves as a new starting point for more sophisticated calculations
and experiments.
