Let
be a compact
-manifold
with boundary a single torus. We present upper and lower complexity bounds for closed
-manifolds obtained as
even Dehn fillings of
.
As an application, we characterise some infinite families of even Dehn fillings of
for
which our method determines the complexity of their members up to an additive
constant. The constant only depends on the size of a chosen triangulation of
, and
the isotopy class of its boundary.
We then show that, given a triangulation
of
with
-triangle
torus boundary, there exist infinite families of even Dehn fillings of
for which we can
determine the complexity of the filled manifolds with a gap between upper and lower bounds of
at most
. This
result is bootstrapped to obtain the gap as a function of the size of an ideal triangulation of
the interior of
,
or the number of crossings of a knot diagram. We also show how to
compute the gap for explicit families of fillings of knot complements in the
-sphere. The
practicability of our approach is demonstrated by determining the complexity up to a gap
of at most 10 for several infinite families of even fillings of the figure-eight knot, the pretzel
knot
,
and the trefoil.