A Formation’s Break Point is equal to half the total
number of the models within the Formation at the start of
the battle – unless otherwise noted, this includes models
that were on the battlefield and off the battlefield, due
to being in Reserve or for another reason. Break Points
are rounded up. Titan and Knight models add their total
starting Wounds characteristic, rather than the number of
models, to the total model count of a Formation instead,
and the current number of Wounds lost counts towards
the Formation’s Break Point.
For example, a Formation with 28 models has a Break Point
of 14, while a Formation with 27 models will also have a
Break Point of 14 (rounded up from 13.5).
HH p63
Automated Sentry: Detachments with this special rule
are ignored for the purposes of calculating a Formation’s
Break Point.
HH p87
In addition,
Drop Pod models are ignored for the purposes of
calculating a Formation’s Break Point.
HH p88
Dedicated Transports are ignored for the purposes of
calculating Break Point.