# What is the net effect from advantage or disadvantage on to hit chance? [duplicate]

For many character build calculations, it is valuable to know how much to hit chance is added by advantage (or removed by disadvantage). This differs depening on the number required for a hit on the die roll.

What is the added (or detracted percentage) for each number, and in particular, what is it for 65% chance to hit, the average number required across tiers of play in the absence of magical weapons?

• Fundamentally related: how does rolling two d20 and taking the higher affect the average outcome?
– nitsua60
May 20, 2022 at 23:42
• May 20, 2022 at 23:50
• @nitsua60: Related? It's an exact duplicate, isn't it? May 21, 2022 at 2:22
• "How does rolling two d20 affect" is hard to use for answering this question - there is [one answer] way down the page that addresses the practical question of uplift on attacks directly, unfortunately that one is not entirely correct (it regards to treating a target of 1 as a 100% success. I'm fine with the closure, and will add the corrected version there. May 21, 2022 at 4:28
• @ShadowRanger not in my reading: this is asking for a specific type of analysis that OP presumably finds necessary, and which isn't necessarily the way one would answer the linked post. For me, probabilities and percentages and the way(s) that people (mis)understand them are wide and varied enough that I saw daylight here. Others disagree(d), and that's fine =)
– nitsua60
May 21, 2022 at 12:50

1 95% 99.75% 90.25% 4.75%
2 95% 99.75% 90.25% 4.75%
3 90% 99.00% 81.00% 9.00%
4 85% 97.75% 72.25% 12.75%
5 80% 96.00% 64.00% 16.00%
6 75% 93.75% 56.25% 18.75%
7 70% 91.00% 49.00% 21.00%
8 65% 87.75% 42.25% 22.75%
9 60% 84.00% 36.00% 24.00%
10 55% 79.75% 30.25% 24.75%
11 50% 75.00% 25.00% 25.00%
12 45% 69.75% 20.25% 24.75%
13 40% 64.00% 16.00% 24.00%
14 35% 57.75% 12.25% 22.75%
15 30% 51.00% 9.00% 21.00%
16 25% 43.75% 6.25% 18.75%
17 20% 36.00% 4.00% 16.00%
18 15% 27.75% 2.25% 12.75%
19 10% 19.00% 1.00% 9.00%
20 5% 9.75% 0.25% 4.75%

Roll to hit is the number needed to roll for a hit. 1 always misses.

The highlighted row is the result for the canonical 65% hit chance.

The change column gives the amount the chance to hit improves in absolute terms with advantage, or worsens with disadvantage.