Calcutating a Monster's THAC0 in Classic Dungeons & Dragons

[JenniferRPG]

I am reading the Moldvay Basic Dungeons & Dragons book, about to do some of my first DM'ing with it.

I am going to make a "monster card" for each and every monster in my dungeon which has all the stats that are in the monster section of the book, but along with another stat to make things easy when it comes time to DM: a Monster's THAC0. (Much like I saw thac0 mentioned in AD&D monstrous manual.)

That way I only have to take the monster's THAC0 and subtract the PC's AC from that player's initiative card, to determine if the monster hit.

Here are the set of formulas I came up with to convert from the monster manual to what I type on the monster cards:

Classic Dungeons & Dragons
Monstrous THAC0 Calculation

[TABLE="width: 500"] [TR] [TD]Number of Hit Dice[/TD] [TD]THAC0 Formula[/TD] [/TR] [TR] [TD]1 to 8[/TD] [TD]20 - Number of Hit Dice[/TD] [/TR] [TR] [TD]9 to 10[/TD] [TD]20 - Number of Hit Dice + 1[/TD] [/TR] [TR] [TD]11 to 12[/TD] [TD]20 - Number of Hit Dice + 2[/TD] [/TR] [TR] [TD]13 to 14[/TD] [TD]20 - Number of Hit Dice + 3[/TD] [/TR] [TR] [TD]15 to 16[/TD] [TD]20 - Number of Hit Dice + 4[/TD] [/TR] [TR] [TD]17[/TD] [TD]20 - 17 + 5 = 8[/TD] [/TR] [TR] [TD]18+[/TD] [TD]20 - 18 + 5 = 7[/TD] [/TR] [/TABLE] Does this make sense what I have done? I can think of a simpler way to do this. I don't want to have to look at that chart every time I roll the attack die. Just want to do a simple subtraction from thac0.

 

[Libramarian]

I think if you're going to the trouble ahead of time to make monster cards it would be easiest to simply copy THAC0 from the monster attack table? It's the 0 column (THAC0 = To-Hit-Amor-Class-0).

I use THAC0 in my 1e AD&D game. I'm running the TOEE so whenever I use a monster for the first time I just look up its THAC0 on the attack table and then use it for the remainder of the encounter (and in future encounters if I can remember it).

It would save a bit of time during play to go through the whole module beforehand jotting down monster THAC0s but I'm too lazy for that

I actually ran levels 2 and 3 off the page without even reading the material first

 

[JenniferRPG]

I think if you're going to the trouble ahead of time to make monster cards it would be easiest to simply copy THAC0 from the monster attack table? It's the 0 column (THAC0 = To-Hit-Amor-Class-0).

I use THAC0 in my 1e AD&D game. I'm running the TOEE so whenever I use a monster for the first time I just look up its THAC0 on the attack table and then use it for the remainder of the encounter (and in future encounters if I can remember it).

It would save a bit of time during play to go through the whole module beforehand jotting down monster THAC0s but I'm too lazy for that

I actually ran levels 2 and 3 off the page without even reading the material first

Yeah I don't know why I overcomplicated things. Basically my set of formulas just creates that chart lol.

So AD&D 1e makes use of the same chart Basic/Expert does then.. Figured there was THAC0 listed in the monster manual of 1e, I know it is for 2e.

Thanks for the help.

Seems like the way the basic book is written, they want you to use the chart to look up every single hit based on monster hit dice and the player's armor. That'd be crazy tedious. They make no mention of thac0 in the book nor simply just subtracting the player's armor.

 

[AngryOgre]

Check out Stars without number, they do a thac0 variant which only requires addition. It's like "20 - monster thac0 + any bonuses + player AC + d20 = 20 or over is a hit". I think. Made the old adventures easier for me.