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"Converting d10 in to 2d6 Question" Topic


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658 hits since 4 Nov 2015
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Comments or corrections?

IGWARG1 Supporting Member of TMP Fezian04 Nov 2015 7:35 p.m. PST

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?

Personal logo Sgt Slag Supporting Member of TMP04 Nov 2015 7:45 p.m. PST

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!

Rich Bliss Supporting Member of TMP04 Nov 2015 7:57 p.m. PST

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.

IGWARG1 Supporting Member of TMP Fezian04 Nov 2015 8:30 p.m. PST

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.

Stryderg04 Nov 2015 8:38 p.m. PST

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.

emckinney04 Nov 2015 8:39 p.m. PST

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.

IGWARG1 Supporting Member of TMP Fezian04 Nov 2015 8:54 p.m. PST

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?

Stryderg04 Nov 2015 9:56 p.m. PST

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.

Personal logo Ditto Tango 2 3 Supporting Member of TMP04 Nov 2015 9:57 p.m. PST

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Personal logo Ditto Tango 2 3 Supporting Member of TMP04 Nov 2015 10:04 p.m. PST

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Mako11 Supporting Member of TMP Inactive Member05 Nov 2015 12:38 a.m. PST

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.

TNE230005 Nov 2015 12:43 a.m. PST

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

Personal logo John Treadaway Supporting Member of TMP05 Nov 2015 4:06 a.m. PST

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

John T

IGWARG1 Supporting Member of TMP Fezian05 Nov 2015 5:52 a.m. PST

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

Chris Wimbrow05 Nov 2015 9:44 a.m. PST

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.

Mako11 Supporting Member of TMP Inactive Member05 Nov 2015 12:29 p.m. PST

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.

Timmo uk06 Nov 2015 12:09 p.m. PST

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

(Phil Dutre)12 Nov 2015 6:49 a.m. PST

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.

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