Battle mathematics for an RPG


I've been working on battle algorithms for an RPG I'm programming, but right now I'm having a tough time on the mathematical aspects of how characteristics such as strength, dexterity, weapon proficiency, armor, dodging, etc. all should interact together.

I've come up with some basic math of my own for a lot of things, but I'd like to be able to see some past RPG math for determining these sorts of things.  Any resources out there on the web that show RPG battle mathematics?
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bcladdConnect With a Mentor Commented:
On-line resources for combat systems are hard to come by. The systems are typically costly to develop (lots of playtesting is required to get the balance right; more on that in a moment).

As suggested above, the d20/AD&D system is well tested and in its fourth or fifth edition (depending on where you start counting). The main books are expensive but spell out the relationship between attributes, skills, and combat very clearly. The data itself is copy-written; that is why you don't find very many pages on the Web explaining THAC0 for all weapons and classes and such. The newer versions are fairly well rationalized.

The GURPS system is a general game system that is entering its fourth edition. A distillation of the rules is available on-line ( but the full rules are only on paper.

The Hero system is another general game system (Champions was one of the first games using it). It is very nice (I spent 4 years playing in a Champions campaign). Didn't find any on-line sources.

Haven't seen the rules yet but Paranoia XP, a new edition of Paranoia is coming (or is) out. I will read the rules because the first edition was so, so scrumptious. Wonder what the Computer will think of the word "scrumptious"? Wonder if it is beyond my security clearance to wonder what the Computer will think? The Computer is my friend.

There was a game out there, Aftermath, that had the best detailed action time rules I have ever seen. They were both detailed and moved forward. Used to play Morrow Project with those rules. I don't know what happened to Fantasy Games Unlimited's stock and I haven't seen a copy of Aftermath on EBay (don't always look that hard so it could be there).

Why is making an attributes system hard? Because of the complex interactions. You don't only have to consider how tough armor is against each weapon; you must also consider the relative cost of each weapon and armor in the game economy. Similarly, the cost of different attributes relative to their benefits is difficult to balance (Hero system had some weirdnesses with their Speed attribute not costing what it should ... at least I seem to remember it being Speed). That is one reason to look closely at existing, tested systems.

Good luck,
rsripracConnect With a Mentor Commented:
From my point of view, I would suggest that most mathematics yo uneed to figure out is creating a nice sudo-random dice generator. The rest you should base the the mathematics/logic of Dungeon and Dragons game (the physical RPG).

I recommend adapting from D&D because their system has been well though out and it is well aged.  Just go out and research some of the basic sets and it'll give you a really good idea.

trollmanAuthor Commented:
Thanks guys for the input...  I've been just seeing the beginning of the nightmare of trying to determine the coding of attributes, battle math, etc. and will certainly try to check some of these resources out.  Might be hard to find game books where I live, but I'll see if any inexpensive ones are on Amazon.

I'll leave the question open a bit longer, to see if anyone else has good net resources describing battle systems.
If possible, you can try ebay, too. Many of the earlier edition (but not first edition or first printing) of these games come up in auctions, sometimes even in big lots that don't end up costing that much. Don't know what the shipping would do to you but...

I would second bcladd's comment.  Definitly worth it, even a 2nd-hand book since I think they are really expensive new (cause it has nice drawing and all, heh).

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