Battle Royale: d6 vs. d20

This week a straight forward question inspires me to take on a bigger debate:

Dungeon Master,

Statistically speaking, in seeking a high rolling die combination, is it better to roll a larger number die or have a larger modifier?


I could have responded to this question in 500 words or less and saved you all some reading, however, this encompasses a much bigger debate that I’ve given a lot of thought to: d6 system or d20? (I’ll try not to get too super cereal, but I’m sure I’ll fail).

First though, let’s answer the question that was asked before giving my unsolicited opinion on roleplaying systems in general.  All we have to do is look at statistics.  Let’s use two dueling characters for our example.

An elf has a Rapier, which they deal 1d6+6 damage with, and a human has a Greatsword that they deal 2d6 damage with, but no modifier.  The average die roll on a d6 is 3.5, so on average, the elf is going to do 9.5 damage, and the human will deal only 7 damage. The maximum damage will be the same (12), and their range will be 7-12 for the elf, and 2-12 for the human.

The modifier takes the obvious win, but it’s important to keep in mind that a +6 modifier on damage may not be that easy to accomplish with a starting character.  I think what this all says for a new player, is think very carefully about your modifiers because they can be powerful things!  If you know you’re going to use a Rapier all the time, do everything you can with your starting Feats and Ability Scores to maximize your hit and damage bonuses.

On the flip side of this though, is something that I consider extremely important when creating a character: make them interesting!  If you spend all of your time, Feats, and Ability Scores constructing an unstoppable fighting machine, you’ll have a very dull, one dimensional character, and if you have a good DM, he or she will be sure to challenge you in as many ways as possible, not just with monsters.

Bottom line: Modifiers are powerful, but don’t be a Min-Maxer!

Moving on now to the bigger question: which system is better, a d6 or a d20 system?


I began roleplaying with the old West Ends Games d6 system, and I will be using it as my example, which I realize is not an example of all d6 systems.  One thing that becomes clear in our above discussion is that the range of possible rolls greatly expands when using certain d6 systems.

If a character has a Brawling skill represented by 5d6, that’s a range of 5-30.  For the same roll to be possible in a d20 system, the character would need an attack modifier of +10, giving them a range of 11-30.  To me, if a character has devoted a great deal of training to a particular skill, it makes sense that their minimum roll would still be relatively high.  In a d6 system, this expertise isn’t as well represented, and more is left up to luck.

Heroic characters should have a very small chance of missing a highly inexperienced fighter with an attack.  With the d6 system, my 5d6 Brawler still has a 20% chance to miss an NPC with 3d6 in defense (an average roll of 10).  In a d20 system, with my +10 attack bonus I have only an 5% chance of failure assuming an average AC of 10 (Math people, please see my replies in the Comments section for clarification on my bad math).

You could argue that the systems don’t scale precisely, and if we try and take this into account, the difference between chance of failure might be close to 5%, still in favor of a d20 system.  5% might not be much, but it’s still something for me to complain about.  On top of this though, adding up all those d6 really slows down combat, more so than rolling against a predetermined number and adding a single modifier to one die.  You need to roll your attack, then they roll their defense, then you roll your damage, then they roll their strength.  It’s just too much rolling, and it also encourages players to cheat, because they know I’m not going to sit there and count everyone’s dice all the time (yes guys, I know you cheat).

A d6 system does have it’s benefits though, particularly for newer players.  It is a much simpler, more straight forward and less complex system (and who doesn’t have some d6 hanging around the house?).  It’s easy to learn, and also very easy to modify to suit your own campaign and playing needs.  This always attracted me to it, but in my modifications over the years, I realized I was moving closer and closer to a d20 system, until I dropped the d6 almost entirely.  What I mainly kept from the d6 system, was the flexibility of character creation and advancement that I loved so much.  I’ve always despised Character Levels and Classes, and haven’t used them in years.

So, bottom line number two: Both systems have something unique to offer, both have their pitfalls, and in the end, you either pick one, or design your own rule system like me.

Super Cereal,
The Dungeon Master

Look out for another Friday bonus blog, in which I take on the ultimate question in life: which came first, the chicken or the egg?

If you wish to submit a question to the Dungeon Master, please e-mail them to, or you can Tweet me a question by hash-tagging me (#askthedm) in your Tweet. And make sure to review the disclaimer.

You can also see me in action in One Die Short.

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13 Responses to Battle Royale: d6 vs. d20

  1. Pingback: Accidental Flirting | English and Philosophy

  2. Zoona says:

    I like your drive to simplify combat, it makes a lot of sense.

    Your math is a bit off, though 🙂 The chance of rolling 10 or less with 5d6 is 3.24%. The chance of 3d6 getting a higher combined result than 5d6 is 6,07%.

    Generally speaking more dice gives more predictable average results. As an example, 3d6 gives exactly 11 12.5% of the time, but 18 only 0.46% of the time. This is due to there being a lot of die combinations that give 11 (e.g. 146, 245, 425) and only one (666) that gives 18.

    Another possibly illuminating example comparing 2d6 and 1d12: If you hit on 4 or more, there’s 75% chance to hit with the d12 and 91.6% with the 2d6. On the other hand, if you only hit on 11 and 12, there’s 16.6% chance to hit with a d12 and only 8.3% chance with the 2d6. So, all else equal, the d12 system gives David better chances against Goliath.

    Check out e.g. to see distribution of rolls and percentages with different dice and plusses.

    • Yes, the previous commentor noted my lack math as well, which I addressed below. But as I said to him, thanks for adding your thoughts. The main points for me are the range of possible results rather than the probability of a specific result, and not having to add up a fistful of dice.

  3. MarylandBill says:

    Umm, its been ages since I looked at D6, but something seems wrong here. You are claiming that 5d6 will loose to 3d6 20% of the time? That just doesn’t parse. I am assuming here that both sides roll, and higher number wins right? For the character with 5d6 to have a 20% chance of missing (well actually 22%, but you get the idea), he would have to have a target number of roughly 14 (tie going to the defender). 3d6 is only going to roll a 14 or better 16% of the time. Heck 5d6 will beat the 3d6 maximum roll almost half the time. Now if the 3d6 for defense is added to a target number my analysis is off (like I said, I am rusty at the d6 system).

    In reality multiple dice of any sort tend to reduce randomness. The odds of rolling significantly different than the average decrease dramatically with more dice. At 3d6 the odds of rolling the minimum is 1 in 215… at 5d6 those odds drop to 1/7776. With a d/20, no matter how skilled you are, there is always a 5% chance of rolling that critical failure.

    • Ask the DM says:

      You’re definitely correct. I’ve simplified things a lot because it doesn’t change my main point. My reasoning goes as such:

      The rolling range of 5d6 is between 5 and 30 (a range of 25). Only twenty of those results (10 through 20) will result in a hit, which leaves 20% of all possible results a failure assuming the defender hits their average roll most of the time. This doesn’t take into account probablity distributions and the higher chances of rolling higher numbers.

      But it does help to illustrate the following:

      In the same above example a +10 modifier on a d20 guarantees the impossiblity of a roll below an 11, which I feel better represents the abilities of a hero (and I also don’t believe in critical failures).

      So the main point: I prefer a smaller rolling range (so long as the maximum roll is the same) over buckets of dice.

      Thanks for weighing in.

      • Ask the DM says:

        Although, I guess in retrospect, this was kind of an unfair and biased way to formulate my argument. So, also thanks for adding the sensibility of probability.

        • MarylandBill says:

          You are welcome. The advantage of a system like d6 is that it tends to produce pretty steady results. The wild 1 or 20 that can really skew results in a d/20 based game (if they treat 20’s as automatic hits/criticals and 1’s as automatic misses/criticals) are far less likely once you get to 3d6 or more. Of course that can be a disadvantage as well :). Still that steadiness is why FUDGE (for example) was built around a 4dF mechanice (essentially identical to 4d3-8).

          That being said, the big disadvantage of d/6 and similar games is adding up the totals. I use to play Champions a lot in college; we would spend an awful lot of time adding up the damage (often 10 or 12d6).

          • Ask the DM says:

            It’s true, it really slowed down combat a lot to add everything up, which was actually the initial reason I strayed away from d6. I use my own homebrew system now, and while I still have the automatic hit/miss with the d20, I’ve kept the Fate Die from WEG’s system, so it’s not automatic unless players roll both a 1 or 6 on the d20 and the d6, so it reduces the chances of those things happening a lot more.

  4. Lindsay says:

    I’ve used both d10 and d20, and I like both. I will say, that if I’m a badass in D&D, I roll one d20 to hit, and then say a d12 or 2d8 or whatever plus modifiers. If I’m a badass in Vampire, I represent my proficiency by rolling an entire handful of d10s. I find that very satisfying.

  5. Kevin Stover says:

    Good post. I also started my role-playing days with the WEG Star Wars system. As I’ve played many, many other systems since then, I’ve found that I really enjoy the Vampire: Masquerade d10 combat system. Especially from a GM standpoint; it’s easy for players to understand and very easy to adjust the difficulty of a roll on the fly. Our playgroup usually has one or two “stats” focused characters/players, so I make it a point to put the group in situations that are very non-combat oriented.

    • Ask the DM says:

      I’ve always been a big fan of more non-combat focused roleplaying, which is one of the reasons I’ve tried to streamline combat, so that one fight doesn’t take up a half hour or more or gametime. I’d like to really give the d10 system a shot at some point, as I’ve heard a lot of positive feedback regarding it.

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