Home » Ancient Posts » To THAC0 or Not To THAC0: To Hit Rolls in Lords & Wizards    
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Chris Harvey

I much prefer a to-hit table, I strongly dislike BAB. Any more than two bonuses per roll get tiresome. 1 bonus for ability bonus, 1 bonus for some environmental effect, and that's it.

Venger Satanis

Anything but THAC0. If you use a % system, include a conversion table.

Do a lot of OSR people still use the to-hit tables?



Checked my copy of chainmail and you are right Platemail requires a roll of 12 to hit on the man-to-man table. So I guess I have no clue as to why one needs descending armor class. Although dealing with AC 2 may simplify the math, dealing with numbers like 0 and -5 does not. Although one form of AC 2 is platemail and shield there are several other ways to have AC 2 (like magic chainmail, bracers, monster hide). So the only point I can see for descending AC is habit and custom, not really good reasons to include things in a new game.


imredave, I'm not sure what you're referring to but the armor classes in Chainmail are ascending. The descending ACs seem to be an arbitrary decision of Daves. If you dig up a copy of Dragon #1, you see Len Lakofka's house rules which include Chainmail's ascending ACs (with 1 being no armor and 8 platemail) combined with D&D's to-hit table. I always point this out whenever someone suggests that ascending AC is a 3e thing.

Dan of Earth

I think of Wizards' World (1983) as what 2e might have looked like in an alternate universe. It uses percentages for attacks, with increments based on XP instead of only level. Might check it out for some ideas:



Ascending Armor Class seems a "natural" choice only if you all see in terms of "Difficulty Level" or "Challenge level" as D20 players do ("when all you have is a hammer…"
I personally prefer descending AC (9 to 0) because of familiarity and because I find single digit numbers easier to apprehend ("AC3? Oh yeah, that's plate armor…" "AC17?? F…ck, whats's that? Plate? Plate plus shield??")
Plus, single digit numbers is a good way to keep the numbers bloat and the bonus creep in check (AC9 is the worst protection, 0 the best you can have without potent magic).
And its easy to make a formula with a to-hit-bonus and Target20


The old thac0, descending armor class nonsense comes from a poor adaptation of the 2d6 chainmail system, where you had to roll snake eyes to hit a guy in platemail. There is little reason in a new game not to use the base plus ascending armor class which is lots easier. Your percentage system is also good, but will slow the game a little due to two digit math.


The original D&D to-hit charts where written as percentages. That's because the d20s back then just had 0-9 twice rather than 1-20, so they were good at generating percentages. It wasn't until later that someone got the idea to color one set of 0-9 with a crayon to make a 1-20. That explain why in the original OD&D books, bonuses were often written as percentages (such as "+10% to hit").

I like the idea of each class getting a small percentage bonus per level (fighters 5%, clerics 4% MUs 2% maybe?) but that will probably cause too many problems with compatibility.

I prefer a table driven to-hit system because you can modify it if you want and you don't have to worry about if there is a formula behind the values.


@-C: I'm asking because I literally do not care. All the D20 methods are the same mathematically (as long as I don't go with to-hit tables with multiple 20s as 1e did). I've never understood why some people feel so passionately that one method is so much better than another, but they do. And since which method used has zero effect on the underlying design of the game (like the color of the paint has no effect on the mechanical design of a house) and I don't have a strong preference, I figure I can do what potential players seem to prefer.

Rachel Ghoul

I have to agree that I'd rather have ascending AC just because it feels like fewer steps to add than to have to check against the chart or mess around with THAC0 or whatever. It feels… intuitive I suppose is the right word.


If you are making it for what other people want, it will be terrible.

Cross Planes

As much as I respect and understand how THAC0 worked, BAB and Ascending AC do the same job and it's easier to grok.

Even, what Gamma World 3 (?) used it.

Zach Thomas

I haven't been playing d&d for very long, in fact most of the blogs I read (yours included) are written by people who have been playing longer than I have been alive, so I do lack a bit of experience, but of the systems I have used I have to say I like descending.

I don't have much of a reason other than I like having the to hit table on my character sheet.

Aside from that I like using the target 20 system for nearly all tasks in my games and I simply can't do that with any other system.

By the way, M74 is what introduced me to the hobby and is what I use to introduce others. Thanks 🙂


I always liked the d% systems.

RuleMaster, I mean RoleMaster, used such a system as I recall, but the one I remember using the most was the old TSR Marvel Superheroes.

Just so, rolling a d20 to hit always had a magic charm, ascending, descending, or whatever… I had a dual colored d20 tho, so I was able to fulfill my need to roll the d20 by coupling it with its inferior brother, the d10, and make even d% rolls feel special.