Mental excercise. Converting the d20 system to d6 - entirely-

Evenglare · May 27, 2012

I have been thinking about converting the d20 system (pathfinder in my case) , to use only d6 for rolls. I am aware of the unearthed arcana's conversion that allows 3d6's instead of a d20. It goes through all the necessary things like lowering crit ranges etc etc. This is all well and good , but i want to go one step further and replace die damage with d6s . Now i figure the easiest way of doing this is simply make the damage die d6 and add some sort of modifier to bring it up to par with the original damage die.

Say your standard longsword has a d8 of damage. Now what i'm thinking is boost up the average after making the d8 a d6. So the average of a d8 is 4 (really 4.5 rounding down), and the average of a d6 is 3 (3.5 rounded down). so to equal out I would simply add a 1, thus a longsword would be d6+1. I figure I can basically do this with everything. I understand that the minimum damage rises and the maximum damage falls, as a d6+1 which rolled a 6 would only be a 7 , where a max roll with a d8 would be an 8. However , I'd believe it would be balanced due to higher min damage.

Has anyone done this , or ever considered it? Is there anything I am missing?.

Also another thing I have been thinking about is opposed rolls in combat, by which I mean rolling an attack roll, and the defender would roll a "defense" roll which would be AC-10. I have always wanted to try it out. I like the idea that a character is actively defending (simulated by the die roll) than it being a target number to hit a person's AC.

amerigoV · May 27, 2012

Green Ronin did the exercise for you - Dragon Age RPG (I think they have generalized it to a stand alone system). It uses 3d6 instead of a d20. I believe all the damage is d6 as well (I would check, but then I would have to get up from my chair and move 3' - not in the mood here on a Sunday morning).

If you enjoy the mental exercise, go ahead. If you really want a ~d6 D&D, check out Dragon Age.

Evenglare · May 28, 2012

I actually do have the dragon age rpg. I just wanted to convert the system itself into d6, feats classes and all of that retaining skills and everything.

Dannyalcatraz · May 28, 2012

I've used HERO - a D6 based game- to do cross-edition "D&D" campaigns. You should be able to do likewise with M&M/Warriors & Warlocks...and because it's a d20 game, all the feats & such will already be in place.

mkill · May 28, 2012

I don't think it's a big deal - just do it. It probably helps to have a conversion table ready just in case. Probably the only thing you'll note is that it doesn't change the game all that much.

Which exact version of d20 do you want to convert?

If it happens to be Pathfinder, I'd change the trained skill bonus from +3 to +1d6 (so you roll 4d6), just for fun.

I'd also consider flattening the math a bit to speed up the game. For example, remove the BAB progression and lower monster AC accordingly.

Probably the best system to use for this project is one that is already rules-light. Old School Hack, E6, 13th Age or the 5E playtest could work.

For defense rolls, search the D20SRD for "players roll all the dice".

Squire James · May 28, 2012

A die roll's average is equal to 1/2(max roll +1). So, add the dice averages together and divide by 3.5 to arrive at the number of d6's, and apply the rest as a bonus to the dice. If the leftovers is 2.5, add a d6 and subtract 1. If the leftovers is 3, add a d6. Otherwise, drop the .5 if it exists.

So the basic D&D dice come out to:

1d4: average 2.5 -> 1d6-1
1d6: um, 1d6
1d8: average 4.5 -> 1d6+1
1d10: average 5.5 -> 1d6+2
1d12: average 6.5 -> 1d6+3 -> 2d6
1d20: average 10.5 -> 3d6

If you don't know the size of the bonus ahead of time, it may be easiest to just add the bonus normally rather than trying to consolidate into the d6 system. The more d6's and fewer bonuses, the more likely average results will occur.

Evenglare · May 30, 2012

Interesting i completely looked over the fact of simply adding another d6 when getting to +3. Thanks !

Evenglare · Mar 1, 2013

Squire James said:
A die roll's average is equal to 1/2(max roll +1). So, add the dice averages together and divide by 3.5 to arrive at the number of d6's, and apply the rest as a bonus to the dice. If the leftovers is 2.5, add a d6 and subtract 1. If the leftovers is 3, add a d6. Otherwise, drop the .5 if it exists.

So the basic D&D dice come out to:

1d4: average 2.5 -> 1d6-1
1d6: um, 1d6
1d8: average 4.5 -> 1d6+1
1d10: average 5.5 -> 1d6+2
1d12: average 6.5 -> 1d6+3 -> 2d6
1d20: average 10.5 -> 3d6

If you don't know the size of the bonus ahead of time, it may be easiest to just add the bonus normally rather than trying to consolidate into the d6 system. The more d6's and fewer bonuses, the more likely average results will occur.

In one succinct post you made the entirety of the d20 system into d6. Awesome.

EDIT: Holy crap, I randomly looked this almost a year later and didnt even realize I made the topic hahah.

DWChancellor · Mar 1, 2013

Something that is easy to miss by focusing on expected outcomes (average outcomes) is that the distribution of rolls is dramatically different for nd6 versus using higher sided individual dice (where n is a number of your choosing). The more dice you use to simulate a larger sided dice the quicker game behavior converges to the average of the dice roll.

For instance, if a character must roll a 10 or higher with a d20 or 3d6, the chance of doing so is 55% and ~63% respectively. Not much different. However, the chance of rolling a maximum total, 20 or 18, respectively with a d20 or 3d6 is 5% and 0.5% respectively (a 10 fold difference).

The overall result is that a 3d6 conversion dramatically reduces the likelihood of success and failure in improbable scenarios (where the characters have to roll very low or very high). Furthermore, you can't linearly translate the two systems to each other as single dice statistics is essentially linear, while multiple dice approach a normal distribution. This is why you see a lot of nd6 systems having extremely dramatic effects when characters roll lots of 1s or 6s... they're rare and memorable events.

This might be an advantage for games focused on character interaction and strong difference in capabilities between characters of differing levels, but is a totally different game from a core d20 systems. The effect would be largest at low levels where characters would be less vulnerable (but would be less likely to achieve improbable success too).

Evenglare · Mar 1, 2013

Yeah Im aware of the probability curves. Infact I did a couple graphs with a d20, 2d10 and 3d6. Honestly, I'd like to play with 3d6 because I have a crap load of casino grade d6s. Also I'm always looking to fiddle with the game.