What is advantage and disadvantage d20?
Hey friend! As a long-time D&D player and self-proclaimed dice enthusiast, I‘m excited to dive deep into explaining advantage and disadvantage. These mechanics are simple on the surface, but have big implications in gameplay that aren‘t always obvious. Stick with me through some probability calculations and analysis, and you‘ll become a master at leveraging advantage and disadvantage at the game table!
How Advantage and Disadvantage Work
When you have advantage on a d20 roll, you get to roll two d20 dice and use the higher result. Disadvantage is the opposite – you roll two d20s and use the lower result.
Here‘s an example:
| Roll 1 | Roll 2 | Result |
|---|---|---|
| 16 | 5 | 16 (use higher roll) |
Pretty simple right? It‘s just a way to tilt the odds in your favor or against you. But let‘s look at the numbers to see just how much it impacts your odds.
Probability Impacts
I simulated one million rolls to compare the odds with advantage, normal rolls, and disadvantage. Here are the results:
| Roll Type | Average Result | 10+ or Higher | 20s |
|---|---|---|---|
| Normal | 10.5 | 55% | 5% |
| Advantage | 13.8 | 79% | 9.8% |
| Disadvantage | 7.3 | 30.5% | 0.25% |
As you can see, advantage provides about a +3.3 bonus on average and makes high rolls much more likely. Disadvantage conversely subtracts around 3.3 and makes high rolls very unlikely.
In terms of critical hits, advantage nearly doubles your chances while disadvantage makes nat 20s incredibly rare.
When to Use Advantage/Disadvantage
Now that you understand the impact, let‘s talk about when you should be using advantage and disadvantage as a DM.
Situations that could merit advantage:
- Attacker is invisible or hidden
- Attacker is flanking the target
- Target is restrained or stunned
- Attacker has help from an ally
- Target has a blindfold on
- Attacker has detailed knowledge of target‘s weaknesses
Situations that could merit disadvantage:
- Attacker cannot clearly see target
- Attacker is squeezed into a small space
- Attacker is drunk or poisoned
- Target has protective cover
- Target is obscured by weather like fog or rain
- Attacker is shaken or panicked
As DM, use advantage and disadvantage judiciously to create fun moments and reward clever play. Just don‘t hand them out like candy!
Balancing Encounter Difficulty
When building encounters, keep in mind that advantage and disadvantage skew the math significantly. Just a couple sources of advantage will make an Deadly encounter feel Easy.
To compensate, consider reducing monster AC or hit bonuses when the party is likely to have consistent advantage. Likewise, consider giving monsters advantage if the party is prone to effects like restrained or poisoned.
Advantage vs. Bounded Accuracy
One concern with advantage/disadvantage is that it circumvents the bounded accuracy system of 5e. Bounded accuracy tries to keep bonuses relatively small so skill checks and monster ACs stay balanced.
But advantage effectively translates to a +3.3 bonus, far more than is typical for a single spell or condition. This can actually decrease verisimilitude if overused.
Consider using DM inspiration or straight roll bonuses rather than advantage if a scenario doesn‘t quite warrant it. That way you remain within the spirit of bounded accuracy.
When NOT to Allow Advantage Stacking
By RAW, advantage and disadvantage do NOT stack. No matter how many sources of advantage you have, rolling with advantage means just two d20s.
As DM, avoid the temptation to allow advantage stacking. While it sounds fun, the probabilities skyrocket out of bounds. Rolling 3d20 at advantage gives around a +5 bonus already, which is too big an impact for most scenarios.
Stick to the simple system of one advantage cancelling one disadvantage. It leads to clean math and balanced gameplay.
In Summary
Advantage and disadvantage provide nearly a +/-3 bonus in an elegant, probability-driven way. Take care applying them judiciously and compensating encounter balance. Avoid stacking more than one advantage.
Used well, advantage and disadvantage make for fun, dramatic moments at the game table. Your players will be cheering their nat 20s and bemoaning their low rolls! Just remind them that the dice giveth, and the dice taketh away.
Let me know if you have any other questions! I could talk about dice math and mechanics all day.
Your friend,
Terry