  We prove the formal degree conjecture for non-singular supercuspidal
representations based on Schwein's work proving the formal degree conjecture
for regular supercuspidal representations. The main difference between our work
and Schwein's work is that in non-singular case, the Deligne--Lusztig
representations can be reducible, and the $S$-groups are not necessary abelian.
Therefore, we have to compare the dimensions of irreducible constituents of the
Deligne--Lusztig representations and the dimensions of irreducible
representations of $S$-groups.
