I know this is the dumbest question in the forum, but my system only requires it, and I'm too un-mathematical to figure this out.

I'm working on a browser RPG that blankets video game concepts with table top concepts. The table top style handles to hit combat rolls, and skill checks. The video game aspects are for actual damage, armour, and magic. It seemed like a good way to manage the system, and output them high numbers people like.

I'm working on Armour, and to hit numbers right now. To hit is TN, it's basically like D&D Armour Class. Except rolls are made on 2d12 instead of a d20.

Every piece of armour has a modifier of 0 or greater.

Okay, I broke the math down into little bits. I think I got it right.

Target has enough armour for TN4.

Combatant with +5 Combat Bonus.

Possible 2D12 roll with +5 Combat Bonus = 7-29

2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24

7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29

0 possible failures - 23 possible successes.

100% Chance to hit.

Target has enough armour for TN18.

Combatant with +5 Combat Bonus

Possible 2D12 roll with +5 Combat Bonus = 7- 29

2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24

7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29

11 failures - 12 successes

52% Chance of hit

Target has enough armour for TN4

Combatant with +1 Combat Bonus

Possible 2D12 rolle with +1 Combat Bonus = 3-25

2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24

3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25

1 failures - 22 successes

96% change of hit.

Target has enough armour for TN18

Combatant with +1 Combat Bonus

Possible 2D12 roll with +1 Combat Bonus = 3 - 25

2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24

3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25

15 failures - 8 successes

34% chance of hit.

The only problem is this is pretty bad mechanics. I need the TNs for armour to stay the same, because they're already pretty low. Any suggestions on this?

Actually, the mechanics aren't that bad. Maybe if I increased the attack bonus just a little bit there would be a slightly better to hit rate on higher TNs. Maybe it's good the way it is. I mean the RP part is freeform in the browser game. Characters don't want to get hit all the time, and this way they'll have a chance at RPing dodges and hits...

What you think?

You should write a software for that task as balancing is as difficult as creating the whole game (Blizzard pushed out balancing patches every week for Warcraft III for example over half a year). That way you could test your "formular" against different settings on each side to see if your formular fits. Im working on a RPG currently too but first handling anything as if it is a traditional PnP for more simplicity. My formulars are only basic linear math formulars because I know DnD and Warhammer very good and it isnt fun for anyone to look into hit and armor tables every 5 seconds even in a computer game. If player dosent know how you calculated the hit and armor chances it fill be frustrated when something happend he/she dosent expect.

Level = sqrt(Exp) / 11

is for example the formular to calculate current level from xp (anything is checked without decimals). This is the balanced formular where I took factor 11 because it turned out that this is a good middle between low level exp gaining and high level play time.