Skip to content

Need help understanding combat (dice rolls, what is the deal with THAC0, etc)


I'm playing through BG for the first time after spending years being too intimidated to try. So far I love it, though I'm very early in. One thing I'm having difficulty wrapping my mind around is how combat functions.

At a high level I get that each attack is a dice roll, and that first there is a roll to determine if you hit, followed by a roll to determine how much damage. I also understand that the game performs these rolls automatically in the background.

I recently turned on the dialogue option to show the rolls. What I don't get is, how do I tell what rolls need to be achieved in order to hit a certain enemy? And what do enemies need to hit me? I see them rolling, but I don't know what's going on. For example:

Kobold: Attack Roll 12 + 1 = 13 : Miss

In that instance, is 12 their dice roll, and 1 some sort of multiplier? How do I tell what number they would have needed to roll to hit me?

I initially thought I would just not bother figuring this stuff out and just go wail on things and hope I win, but I figure I'm not going to be able to effectively plan my moves, upgrades, combat pairings etc if I don't get this stuff.

Thanks so much!

PS: In the above example, I had just wandered into Ulcaster and got slaughtered by a bunch of kobolds and skeletons!


  •  TheArtisan TheArtisan Member Posts: 3,277
    THAC0 stands for 'To-Hit Armor Class of 0', in other words, the minimum roll needed to hit an opponent with 0 AC. Suppose you had a guy with 20 THAC0 attacking a guy with 10 AC. He would need to have an attack roll of 10 or above to land an attack.

    Attack bonus add to the attack roll. If the guy with 20 THAC0 was wielding a long sword +2, the +2 gets added to the total, so he'd only need to roll 8 or above.

    A roll of 1 is a critical miss, which always misses regardless of stats, and 20 is a critical hit, which always lands and deals double damage.

    Attack rolls use the formula: d20 + attack bonus = attack roll.

    Of course, I might be wrong about this. I haven't read the manual in ages.
  • outontheporchoutontheporch Member Posts: 4
    Ok I think I get that. So is there a way to know what the AC or THAC0 is for enemies? If not then I don't really know what I want to roll in a battle right?
  •  TheArtisan TheArtisan Member Posts: 3,277
    No, you can't in the game. There's no real guideline for how much combat stats you need besides 'low AC and THAC0 is good'. You can estimate it with a wide range of different rolls but that's the most you can do.
  • GallowglassGallowglass Member Posts: 3,356
    If you install some editing/modding tools, then yes, you can look in the game files and see what stats (inc. AC and THAC0) any creature has.

    Natively in-game, however, no, you aren't told your enemy's AC or THAC0. Nevertheless, with a little experience, you should quite rapidly find yourself developing a fairly accurate feel for enemy capabilities, from "these guys are soft as butter, any old roll will do" to "this is one tough hombre, I'll need a good roll here".
  • outontheporchoutontheporch Member Posts: 4
    OK I think that makes sense! So I just need to keep getting better by:

    - Improving my AC
    - Improving my THAC0
    - Improving my weapons (getting gear that gives bonuses, has better dice range)

    And I'll know I'm too low level if I don't seem to be winning any rolls, and none of my stuff lands. After that, it's all about strategy, positioning my party right, using the right spells and abilities against the right enemy types, etc.

    That sound about right? I really want to get this!
  • GallowglassGallowglass Member Posts: 3,356
    Yep, that's exactly how it works.
  • BillyYankBillyYank Member Posts: 2,768
    Also, pay attention to your proficiencies. You get a pretty hefty penalty for using a weapon you're not proficient with.
  • SirBatinceSirBatince Member Posts: 882
    edited January 2017
    If you want a standard reference, in bg1 you are essentially invincible at -4. Obviously that's just in theory; criticals and spells will still harm you.

    Some opponents are extremely accurate and they'll make even -8 look poor, but they're usually rare, alone or they have a special appearance / role that warrants them being strong.
Sign In or Register to comment.