At what point does a + bonus to die rolls become better than Advantige?

[harken23]

My math(s) skills seem to fall just short of figuring this out. But if you're rolling a 20-sided die, and have to choose btw, say, +1d4 OR advantage, what do you pick? How much of that depends on the DC? Like, if the DC is 2, you're obvs better off using advantage, bkz the chances of rolling snake eyes is 1 in 400. But if you need, say, a 12, or an 18, are you better off taking the +d4? Or using advantage? If you need a 30, I guess you're better off taking as many boni as you can....

[BlazeRomulus]

always advantage of course, even better if you get to add the +1d4 WITH advantage as well.

Edit: you mentioned the odds of rolling snake eyes is 1 in 400, well I did, once.
I think if you really want to have "advantage" is to make sure you have inspiration points for whatever important check you are making.

[Bloodwest]

i prefer advantage over +1d4 flat bonus, i suppose it's just better than nothing. flat bonus lowers the min roll you require to succeed but if you already have bunch of bonuses on top of it, rerolls give little to no chance for failure.

[Hobocop]

BG3 has the natural 20 autosuccess and natural 1 autofailure rule which skews things in Advantage's favor. Especially if your flat bonuses with a d4 added won't meaningfully affect a very high or very low DC check.

[Emilia Tempest]

Advantage is always better unless you can make the roll fail only on a Nat1
though if its a +1 compared to advantage, advantage always wins due to increasing your odds to win the check way more

But if you can, lets say, add a +5 or more (assuming you arent over the DC yet, like you need a 15 and only have 5 so adding +5 is pretty good, but if you have 14 and get a +5 then its mostly wasted) then its better than advantage, however I dont think there is any singular buff that gives +5 to something part from maybe strength checks with a Cloud Giant Potion on a low Strength char. A 1d4 isnt reliable enough to beat Advantage

[Zsrai]

If I remember the numbers properly from discussions around Warcaster vs Resilient: CON, the former is worth about 3-3.5 bonus on average, so proficiency (+4 at level 9) is better than Advantage.

Seems like your answer for Advantage vs +1d4 is going to be Advantage unless you feel like gambling on that d4 roll.

[CEO of Genrush]

+1d4 is better for DC 19-21
+1d6 is better for DC 17-23
+1d8 is better for DC 15-24
+1d10 is better for DC 9-26

+1 is better for DC 20
+2 is better for DC 19-21
+3 is better for DC 18-22
+4 is better for DC 6, 16-23
+5 is better for DC 6-10, 12-24

(unless I made a mistake somewhere)

[guard65]

Originally posted by funny_bean1v1:

+1d4 is better for DC 19-21

That sounds close to me.

Advantage is a moving target based solely on where the to hit or DC save falls, when looking at the % odds of its advantage. That + equivalent verse advantage equation is just as much a moving target. The high the DC the higher the + value must be to compete, to be equivalent to advantage.

[Hex]

Advantage is always better, if you have to choose. The chances of rolling a 1 is halved, while the chance of a crit is doubled.

[AokiYakumo]

Hang on, lemme do some maths.

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Most DCs won't exceed 30 in this game save for the impossible DC 99.

Under most circumstances (unless you're Happy Asty speccing into Sleight of Hand) your skill bonus won't exceed +13 innately (i.e.: without buffs or item boosts).

Since you have 20 possibilities, with one possibility being auto-pass and one being auto-fail. On a DC 2 with a bonus of +0 you have a 95% success chance at base, a 99.75% chance with advantage, and a 90.25% chance with disadvantage.

Guidance (+1d4) will add an average of 12.5% to your success chances, capping at the chances listed above (if you have a +14 against a DC 17, you'll go from 90% to 95%, 100% of the time, but if you have a +12 to a DC 20, you go from 65% to 77.5% on average).

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Knowing all of this, we basically need to find the cutoff for when Guidance will add - on average - more of a chance to succeed than rolling twice and taking higher.

Which basically tells us this: If the difference between your skill bonus and the DC you need to beat is less than 18, then Advantage generally is the better bet, netting a higher chance to succeed from between 0.3% and 12.5%, the closer you get to the difference of your skill bonus and the contested DC being 11.

18's a magic number here, considering you only need to be 2 points away from the DC to be able to pass on anything but a 1. 18 is the exact number of possibilities on the d20 where a chance to succeed and a chance to fail can co-exist.

This means Guidance, on its own, actually won't impact much unless it's added to force the "auto-pass" (you add it to make sure Nat-1 is your only point of failure).

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Now, as you spike up to d6, d8, and d10 (Bardic Inspiration), the number difference drops significantly. With a d6 bonus, the average difference where Advantage wins out changes to a range of between 6 and 16. With a d8, it changes to 8 to 14. If you can add a d10, it can actually swing the die roll more in your favor than advantage ever would (since the average of a d10 is 5.5 which is a +27.5% modifier to your chances, and the highest swing you get from advantage is 25% at a difference of 10).

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TL;DR: mathematically, advantage on a die roll is going to be between slightly better and MUCH better than +1dX on a die roll, unless your adding +1d10 or better, in which case add that before advantage.

[Jarsonne]

Advantage bonus is dependent of base chance so net DC (DC - bonus), unlike extra dice bonus giving a fixed extra chance past for case over the limits. So I don't get why d10 giving an average extra 27.5% chance is better for any DC - bonus value.

[Chaosolous]

I almost always opt for advantage. The only time I don't is if it's not pragmatic or if you're playing a high level thief with that "No roll can be less than 10" skill. Thieves that have that skill usually can roll pretty high once their bonuses are applied to it. I could easily hit 30+ with my thief.

[AokiYakumo]

Originally posted by Jarsonne:

Advantage bonus is dependent of base chance so net DC (DC - bonus), unlike extra dice bonus giving a fixed extra chance past for case over the limits. So I don't get why d10 giving an average extra 27.5% chance is better for any DC - bonus value.

Because 50% ^ 2 is 75% (this being the difference of 11 between the contested DC and your skill bonus, i.e.: the minimum number you need to roll to meet & beat the DC), which is a 25% difference; but a d10 is +5.5, which on a d20 is a 27.5% difference.

I can show the chart if you like to see the numbers behind it, if you like.