The Wc calculation is:

class Wc minus THAC0(STR) minus weapon Wc minus level minus 1 every 6 levels

Where THAC0 is found using the STR stat on table primary stat effects,
the weapon's Wc can be determined from the Crossfire Spoiler
and the level is taken from the physique experience categories.

The lower the WC , the better.

Weaponless attacks like the four combat skills clawing, flame_touch, karate and punching have also a Wc .