  R\"odl, Ruci\'nski, and Szemer\'edi determined the minimum $(k-1)$-degree
threshold for the existence of fractional perfect matchings in $k$-uniform
hypergrahs, and K\"uhn, Osthus, and Townsend extended this result by
asymptotically determining the $d$-degree threshold for the range $k-1>d\ge
k/2$. In this note, we prove the following exact degree threshold: Let $k,d$ be
positive integers with $k\ge 4$ and $k-1>d\geq k/2$, and let $n$ be any integer
with $n\ge k^2$. Then any $n$-vertex $k$-uniform hypergraph with minimum
$d$-degree $\delta_d(H)>{n-d\choose k-d} -{n-d-(\lceil n/k\rceil-1)\choose
  k-d}$ contains a fractional perfect matching. This lower bound on the minimum
$d$-degree is best possible. We also determine optimal minimum $d$-degree
conditions which guarantees the existence of fractional matchings of size $s$,
where $0<s\le n/k$ (when $k/2\le d\le k-1$), or with $s$ large enough and $s\le
n/k$ (when $2k/5<d<k/2$).
