All About THAC0

[tkdco2]

While these videos focus on 2e, the principle applies to OD&D and other pre-d20 systems. Pretty good explanations.

THAC0 Explained



Why THAC0?

[soundchaser]

Handy. Thanks for the links.

[Finarvyn]

THAC0 happened during a time when I was buying AD&D books but apparently not reading them carefully, so I was really slow to think through the THAC0 process and had come up with alternates that I liked better than THAC0. It's probably a great system, but it always seemed backwards and counter-intuitive to me. Nice links, however, for those who want to examine the mechanics behind 2E.

[thomden]

This is probably the best explanation of THAC0 I've seen. Remembering that you always only have to get your THAC0 number or higher, after adding & subtracting all the modifiers is easy enough. It's funny that THAC0 is seemingly easy, but in practice it is just kludgy enough to trip up even experienced players. Every time I use it I have to pause and think for a moment.

[doublejig2]

...and kludgy enough for a trip of even experience. When it occurs, think vogue!

[owlorbs]

Thac0 – Attack Roll = Armor Class you hit

There, I did it in less than 15 minutes.

(I jest, I watched the vids because I was a big 2e lover).

[tkdco2]

The first mention of THAC0 was actually in the 1E DMG. It's included in the monster list. Also included is the XP award for defeating each monster, strangely excluded from the Monster Manual.

[tombowings]

Don't forget that the MM was published long before the PH and the DMG. The MM is very similar to Holmes basic.

[Zenopus]

Including XP values with the monster stat blocks only appears obvious in hindsight. The Monster Manual was still following the OD&D paradigm where XP values are calculated using the table. Even B/X still lacks the XP values in the stat blocks; it first appears in the Basic line in the Mentzer sets.

[soundchaser]

We default to XP for gold, and I use HD multiple for the monster XP if we want that route. I really just like d20+FA/BAB+modifiers+AC, THAC0+ to hit. So easy. BTW, I think the "reasons" in the cited videos are cleverly thoughtful.

[howandwhy99]

I agree with much of the video but I disagree with a few points. But then I prefer To Hit charts for character sheets.

The double row with multiple columns to list your Die Roll versus AC hit.

Then the player can simply roll, perhaps add some modifiers (magic, Str, etc) and check the chart telling the DM what AC he hit, or so he thinks.

Then the DM only needs to focus on any and all of the situational and environmental modifiers to the player character. And potentially any unique modifier like a cursed sword the player doesn't know they have.

This allows the players to routinely play the "What's their AC?" game, and also notice discrepancies between individual characters hitting or not hitting. You could even notice you might have a magical sword (to hit bonus) you otherwise didn't know.

No heavy math, with players doing the chart lookups. Of course DMs have to look on their big charts for all monsters (by HD & level or class type & level), but you get used to it.

This goes back to the experience you can see in TV and movies from the day. DMs doing math while studying the battlemat and DM screen to confirm modifiers to the attack. And players checking their sheets when rolling to check their characters To Hit chart.

Edit: There still remains the possibility of players lying about the math. Or chart lookup. Or even the dice rolls. "Oops! I made a mistake" So some DMs will only want the raw number rolled. And knowing how to do the math helps.