  Spectral ordering between dark and bright excitons in transition metal
dichalcogenides is of increasing interest for optoelectronic applications.
However, little is known about dark exciton energies and their binding
energies. We report the exciton landscape including momentum-forbidden dark
excitons of MoS$_{2}$ monolayer using single shot GW-Bethe Salpeter equation
(G$_{0}$W$_{0}$-BSE) calculations. We find the lowest-energy exciton to be
indirect at ($\textrm K'_{v} \rightarrow \textrm K_{c}$) in agreement with
recent GdW-BSE calculations [2D Mater. 6, 035003 (2019)]. We also find that by
large, dark exciton binding energies ($E_b$) scale with the quasiparticle
energies ($E_g$) according to the $E_b/E_g=0.25$ rule. Differences in exciton
binding energies are explained using an orbital theory.
