Don´t read this give awnser!!!(hahahha)

To
Hit
Armour
Class
Zero

Except that THACZ is a crap acronym, so we get THACO.

The maths:

hit roll = THACO(attacker) - AC(defender)

So you take your thaco, subtract your opponents AC and if you can beat that total on a D20 then you hit. Normaly modifiers like weapons bonuses and fatigue are added into your THACO as well.

So if my THACO is high and my AC is low i have a good chance to win?

THACO low, good.
THACO high, bad.

Some examples... ...

Enemy has an AC rating of -2

P1's THACO is 20, 20 - (-2) = 22. He needs to roll a critical strike(20) on a 20-sided dice(d20) to hit the guy.

P2's THACO is 10, 10 - (-2) = 12. Anything that is 12 and above from a d20 roll is a hit.

P3's THACO is 0, 0 - (-2) = 2. Short of a critical miss(1), any roll from a d20 is a hit.

Just a bit more on Dundee's response...it implies this but I'll say it straight out

When rolling to hit, a natural 20 (critical hit) will ALWAYS hit, no matter what you're swinging at (you could have a THACO of 30 and them have an AC of -20, you'll still hit on a 20).

A natural 1 (critical miss) will ALWAYS miss, even if they've got an AC of 10 and you've got a THACO of -30. In AD&D it also penalized your character, but I don't know if the game impliments that.

Also remember that is YOUR THACO vs your OPPONENTS ac.

The last word on "Natural 20s" and "Natural 1s":

Certain weapon styles (Single Weapon and Two-Handed Weapon) will enable you to score Critical Hits on rolls of 19, as well as 20.

Not only do Critical Hits always hit, but unless the victim is wearing a helmet or otherwise protected from Critical Hits, the damage from your blow is doubled.

Rolling a Critical Miss imposes a slight delay before you can attack again--much as if you lost your balance during your swing. If you are in Stealth and you roll a Critical Miss, you will instantly become visible.

Thanks guys!!!! [img]graemlins/wizardtrouble.gif[/img]

note that helmets only prevent the doubled damage, not the automatic hit.

In AD&D, your critical miss penalty is up to your DM. For BGII, it just doubles the time it takes for you to make another attack.

In ALL of AD&D (2nd ed.) LOWER IS BETTER!! Saving throws, Thac0s, ACs, etc. should all be low. (note the obvious exception to the low-good rule is level... :D )