"Converting d10 in to 2d6 Question" Topic

Probably a question for more mathematicaly inclined than me. Say the morale # to pass is 7+ on 1d10. I want to convert morale rolling in to 2d6 instead of 1d10 to keep just 1 type of dice in a game. Should this morale stay 7+ for 2d6 or should it become 8+ or something similar because of more variables for 2d6?

Adding dice results together, yields a bell curve of results, meaning you will get more results in the middle of the range. A single die, or results not added together, will give a flat chance of any single result. I would not shift the goal number much. Cheers!

You're better off converting the 6 sided rolls to a d10. For example rolling a 4 or better on d6 is the same as rolling a 6+ on a d10.

No, d10s give too much amplitude when rolling for combat in my rules. That's why I want all d6's for all the rolls.

You could roll 2d6, but read them as separate results:
1st d6 determines how to read the 2nd die:
1-3 = low, 4-6 = high

2nd die: if low = 1-5 (re-roll 6's)
2nd die: if high = (1-5)+5 (re-roll 6's)

Still gives a flat distribution, you just have to ignore 6's on the 2nd die. Probably easier to show you than explain it, though.

What is your real question? Are you asking what the closest mathematical equivalent for 7+ on d10 is for 2d6? Or are you asking how to scale things so that the same modifiers have approximately the same effect? Or something completely different.

I am asking:

– a unit has to roll 7+ to pass morale on d10. If I roll 2d6 instead, should it still be 7+ or should it be some other number to retain/reflect the same chance?

There's a 40% chance of rolling 7+ on 1d10.
There's a 41.2% chance of rolling 8+ on 2d6.
That's as close as you are going to get.

Most of the above values are pretty close to results in various outcomes of tens of units, in percentages, so I don't see why not, ignoring the very highest and lowest results, of course.

reasonable approximation
results on 2d6 for a given % chance of success

5% 11
10% 9
15% 6
20% 7,12
25% 4,7
30% 7,8
35% 2,4,5,6
40% 5,6,8
45% 6,7,8
50% 4,5,6,7
55% 5,6,7,8
60% 3,5,6,7,8
65% 4,5,6,7,8
70% 3,4,5,6,7,8
75% all except 2,3,4,10
80% all except 2,4,10
85% all except 3,11,12
90% all except 9
95% all except 11

7+ for success on a d10 is 40%
roll 2d6, a result of 5, 6, or 8 is success

I'd just use a d10: the maths seem painful

John T

Thanks a lot for the help! Those tables will be very helpfull!

If you use 2d6 with different sizes or colors, you can read them as 11, 12, 13, 14, 15, 16, 21, … 56, 61, 62, 63, 64, 65, 66.

This gives 36 possibilities. You can divide them into even ranges of 3 (simulating a d12) or ranges of 4 (simulating a d9.) Treating doubles as something special leaves you with a simulated d30 which can be ranged as a d10. And you can make any range of numbers more or less likely.

For 5% increments, I recommend the D20.

It rolls very nicely too, in order to make back to back re-rolls of the same number far less likely.

Thanks for this – it will help me resolve a firing table I'm experimenting with.

anydice is an excellent tool to do an analysis like this.

Probabilities of rolling a minimum number on 2D6:

2 100.00
3 97.22
4 91.67
5 83.33
6 72.22
7 58.33
8 41.67
9 27.78
10 16.67
11 8.33
12 2.78

Probabilities of rolling a minimumnumber on D10 (rather trivial):

1 100.00
2 90.00
3 80.00
4 70.00
5 60.00
6 50.00
7 40.00
8 30.00
9 20.00
10 10.00

Now match both tables as close as possible, and you have your conversions.