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Message: <blockquote data-quote="Esker" data-source="post: 7891300" data-attributes="member: 6966824">I'm not sure why you're focusing on the difference in spacing... In 5e's d20 system, the only thing that's relevant is your chances of meeting or exceeding some threshold; it doesn't matter at all how likely you are to roll any specific value, X, except insofar as that represents the difference in difficulty between a DC X and a DC X-1 roll.The OP's suggestion was that using 3d6 is similar to a system where where bonuses are doubled, DCs (and similarly, ACs) are transformed to be DC' = 10 + 2*(DC - 10), and we use a d20 to resolve outcomes. Note that this is the same in practice as taking the new DC to be 10.5 + 2*(DC-10.5), where we've used the actual expected value of the 1d20 and 3d6 rolls, because this is 0.5 lower than 10+2*(DC-10), and so it yields success on the same integers.If you need a natural X to succeed in the 3d6 system (that is, you have a +Y bonus and the DC is X+Y), that becomes a +2Y bonus and a DC of 10+2*(X-10)+2Y. So you need a natural 10+2*(X-10), or 2*X - 10 in the modified d20 system. So we could compare success rates for each value of X with the corresponding target natural rolls.Alternatively we could leave bonuses and DCs the same and scale and shift the roll instead. Compare 1d20 to 2*3d6-10. Using a target of X on the 2*3d6-10 roll is equivalent to a target of ... 2*X-10 on the modified d20, just the same as if we'd rescaled bonuses and DCs.So the OP was off by one in their graph in terms of illustrating the impact of their proposed system relative to using 3d6 with regular bonuses and DCs. But actually using -10 vs -11 only affects which system makes for easier rolls, not the sizes of the gaps, since 10 and 11 are equal distances from the mean, and so you're essentially just swapping successes and failures and inverting the labels on the x-axis.</blockquote>

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