The critical chance bonus from aiming is (60+4*luck)/100*BodyPart
By BodyPart I mean the bonus you get from aiming a particular body part with 10 luck:
Eyes: 60%
Head: 40%
Arms, Groin: 30%
Legs: 20%
Torso: 0%
So, saying you have 1 luck and you aim to eyes, you have:
(60+4)/100*60% = 38,4%
Then, to that calculated value, you add base critical chance(which is displayed in the character tab, it's luck + More Critical bonuses, i. e. with 1 luck and 1 more critical it's 6%).
I don't know how bonuses from HtH perks and attacks(like Haymaker) are counted.
Hit chance there:
http://www.fo2238.fodev.net/wiki/Hit_Chance