Many budding war game designers spend a great deal of time
talking about mechanics, especially using dice.
It is only natural since dice mechanics are the “crunchy” part of
war game design. The only other topic
that can compare in the “crunch” department are points cost or balancing
mechanics. Therefore, it is an easy
topic to discuss.

**This is not the first time I have tackled it on the blog**.
The “Best Type of Dice” to use is a frequent conversation
piece. Lately, the humble d6 has fallen
out of favor with many designers. The
main reason is the available range of numbers that a d6 can generate, and the
probabilities it can simulate are limited.
Keep in mind as we proceed that I am not a mathematical genius or expert
on probability. In fact, I am just a
humble war game blogger….. pretty unexciting expertise.

**Cons**

So, let’s start by talking about the Cons of the d6. As mentioned it can generate only 6 actual
results. This is much lower than a d10
or a d12, or even a d20. Therefore, there
is a much smaller range of numbers to work with and this makes differentiating
of success and failure much harder.

Essentially, you have a 16.67% chance of getting any
individual result. Therefore, if you
need a 6 to do something, you will only score that 6 16.67% of the time. If you need a 4, 5, or 6 you have a 50.01%
probability. 16.67% is not very fun to
calculate with, but 50% is fine. What
about 5+ then? 33.34%. Compared to the d10 and their 10% increments,
the d6 is far inferior for calculating outcomes and running the numbers
quickly. The same can also be said about
a d20 AND it adds more possible outcomes.

Every modifier of + or – 1 adds a 16.67% variability in
the outcome. That is a big swing between
potential outcomes made by relatively simple modifiers. This means a -1 penalty is a big reduction in
efficiency for a dice roll and a +1 is a huge gain. Those large swings can be hard to moderate
for.

**Pros**

With those clear deficiencies, why would anyone want to
continue using a d6 as their primary dice?
Are they insane or just stupid?
Neither, as the humble d6 also has its benefits.

The first is that they are common and easy to get. Custom dice or other polyhedron dice raise
the barrier of entry for a game. Granted,
if your core audience is “experienced” gamers only then this does not
matter. However, most games are trying to
appeal to the widest audience possible to garner use. Everyone can get or has access to the humble
d6. I see that for sale in packs of 5 at
the local gas station for less than $1 USD.
They are ubiquitous and have been in use for centuries.

Once you start adding multiple d6 together, you have a
very nice and simple bell curve of likely results. Rolling two single pips has only a 2.78%
chance, while rolling a combination that adds up to 7 is a 16.67% chance. 16.67% is actually the highest result you can
get on 2d6 so you are statistically most likely to roll a 7. This bell curve allows a designer to
accurately predict outcomes than any single dice.

Combined 2d6 also gives you same amount of potential
results as a d10, without the “randomness” of any 10% option coming up. You know a 7+ combination will come up more
often than a 10+ combination on 2d6. 7+
is 58.34% on a 2d6, while 10+ is 16.67%
Meanwhile, on a d10 a 7+ is ~40% and a 10 is 10%. Curves provide more predictability than a straight
line chance, which allows a designer to “stack the deck” with modifiers to
create

**tactical play**in a more meaningful way.
What happens when you start adding multiple dice to d10’s
or d20”? The more numbers you add, the flatter
the curve, and you the less predictability it adds to the curve. For example, 2d10’s most common result is an
11 at 10% and the equivalent roll on a 2d6 is 16.67%. 2d20 is 21 at only 5% which is the same as a
single d20 result, so why roll 2 d20?
2d6 gives you the most “dramatic” bell curve.

There is a reason d6 have been the most common types of
dice for centuries. They provide a
dramatic and interesting probability curve that other dice can not match in
groups. The closest is the d12, and

**I can only think of one designer**who really stresses the use of a d12. Even that is just a derivative of a d6.**Why So Many Single D6 Games Then?**

Okay, so maybe I have convinced you that 2d6 is the
ultimate dice to roll for your mechanics.
Then why do so many games use a single d6 resolution mechanic? I would argue that very few of them actually
do use a single d6 resolution mechanic.
They almost all temper it with some sort of multiplier….. let’s take a
closer look at some mechanics in games.

Arguably, the most familiar of the game systems that is
based on a single d6. However, to determine
a hit from shooting you take a model’s shooting skill and subtract it from 7 to
get the target number needed to hit. If
you have a shooting skill of 4, you need a 3+ to hit. If you have a shooting skill of 3 you need a
4+ to hit. Therefore, a shooting skill
of 4 vs. 3 is 16.67% better and more “lethal”.

However, you will notice that it takes more to
incapacitate your target in Warhammer 40K than a shooting roll. They mitigate the odds by adding two
additional rolls for wounding and a potential saving throw made by the defender. Therefore, to remove a single model, you are
really rolling 3d6 looking for a series of target numbers. It is not resolved by a simple d6 roll at
all. AS the probability for each roll
result is added in, the likely outcome from the series is reduced.

In Lion Rampant, they use a single d6 per model compared
to a stat to determine if a “hit” is caused.
Therefore, a model with a shoot skill of 5+ will “hit” a target with a
33.34% likelihood of causing a hit. However,
when you look closely at the rules, you will see you roll a d6 per model so you
are typically rolling multiple dice at a time.
In addition, the number of hits are compared against a units’ armor to
remove targets. Armor can be modified by
range and terrain. Therefore, the key arbiter
of lethality is armor rating and not just a single d6 roll.

This game also only uses the humble d6. However, it uses them in opposed dice pools. The target number is always 4+ on a dice to get a success and then you compare successes to determine opposed tests. In addition, the game has no negative modifiers. Instead, extra dice are added as a bonus.

For example, if a hero is behind a wall, their is no reduction in dice for the villain shooting at them. Instead, the hero gets extra dice to resist or dodge the attack. The probabilities come from the number of d6 rolled against each other, minimizing unknown outcomes with the more dice that are rolled. However, the small element of chance is still in play.

For example, if a hero is behind a wall, their is no reduction in dice for the villain shooting at them. Instead, the hero gets extra dice to resist or dodge the attack. The probabilities come from the number of d6 rolled against each other, minimizing unknown outcomes with the more dice that are rolled. However, the small element of chance is still in play.

**Final Thoughts**

The humble d6 has been the dice of choice for centuries
because it offers the most dramatic, yet predictable probability curves for
game designers to play with. Combine
various mechanics to group dice and combine probability curves from a d6
results allows for a wide variety of game play options.

Ultimately, very few people play a game because of its
dice mechanics. Instead, they play games
that set out to model or do certain things that the players find
appealing. As a designer, the dice
mechanics are simply a tool to try and reflect the “reality” of your game and
accomplish the goals you have set out for the game itself. The specifics of the dice mechanics are
secondary to that goal. As a designer,
you need to use the tool that meets the games goals whether that be d6, d10,
d12, or d20s. Mechanics for the sake of
mechanics are an empty and hollow exercise.

I rather like the limited range of the D6. The big jumps in probability between the numbers provide clear & simple outcomes where differences actually matter. At least if you stick to 1 to or 2 D6 per roll. And it doesn't have to mean your game is simplistic. You just have to be more creative elsewhere in your rules. The sophisticated action & counter-action system of Rogue Planet (which uses 2D6 and limits modifiers to +3 & -3 maximum) would be a nice example.

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