With the release of Dungeons and Dragons 5th edition came the new mechanic of advantage and disadvantage when you rolled ability checks or attack rolls. What is advantage, what does advantage mean and how does it affect your odds?
Divine spells, monstrous creatures, skills, player classes and many other aspects of Dungeons and Dragons can be affected by advantage.
What is advantage and disadvantage?
What is advantage? Simply put, if you have advantage when you’re making an ability roll, you get to roll two D20s and you pick the HIGHEST.
What is disadvantage? It should come to no surprise that disadvantage means you roll two D20s and pick the LOWEST.
It’s a simple mechanic, easy to pick up, apply and remember.
Advantage can easily be handed out by the DM, they no longer need to think:
Would this situation grant the player a +2, +4 or a +6 bonus to their roll?
The DM can easily just say:
You’ve got advantage to that next roll
Just as its easy for the DM to hand out advantage or disadvantage, it can be added as a side-affect to spells, feats and skills.
Maybe that powerful staff you’ve given out grants the wielder advantage on every attack under a full moon.
Maybe you created a magic item with advantage, not knowing quite how it affects the odds. Now the players are unstoppable, landing attack after attack. If this is the case, read here on how DMs can handle overpowerful items.
Equally it can be added to monsters under special circumstances, for example, a doppleganger has advantage on all attack rolls against any creature it surprises.
What if you have both advantage AND disadvantage
If you are granted advantage for one reason but receive disadvantage for another, they cancel each other out.
It is important to note that they don’t cancel each other out 1-for-1, if you have any amount of both, you just make a single D20 roll.
What’s the real bonus from advantage?
What is advantage? We now know advantage is the best of two D20 rolls, but how does that affect the average dice roll?
A single D20 will produce any given number, on average, 5% of the time (1/20th)
That is, you’re just as likely to roll a 20 as you are a 1.
However when you roll 2x D20 and pick the highest, for advantage, the odds of getting a 20 as your result are higher than that of a 1.
Getting a 20 as a result of advantage
As mentioned above, a natural D20 rolled once will get a 20 as a result 5% of the time.
Rolling a 20 with advantage. In fact with advantage you’ll roll a 20 almost 10% of the time. That’s, not surprisingly, almost double you’re normal chance.
Rolling a 20 with disadvantage. Sadly, if you’re looking to get a critical hit and you have disadvantage, you’re only going to get it 0.2% of the time.
Thankfully most of the time you’re not looking to roll a nat’ 20.
Getting 15 or higher as a result of advantage
A DC15 roll is fairly standard for both ability checks and attacking enemies.
Normally with a D20, you’d roll 15 or better 30% of the time.
Rolling a 15 or higher with advantage. Here we see a huge swing in your favour. Rolling a 15 or higher with advantage will happen almost 51% of the time! So you’re actually more likely to succeed than you are to fail.
Rolling a 15 or higher with disadvantage. Needless to say, with disadvantage you’re only going to be succeeding 9% of the time. Ouch.
RS Conley from RPG stack exchange sums up what the D&D 3rd edition dice +/- modifier would be to roughly equate to advantage/disadvantage:
The general rule of thumb that in the mid range of the d20 (from success on a 9+ to 12+) advantage grant roughly a equivalent to a +5 bonus and disadvantage a -5 penalty. The increase and decrease in odds tappers off when your odds of success approach 1 or 20. For example a advantage on a 19+ your chance of failure goes from 90% to 81% not quite a +2 bonus on a d20.
So if you’re trying to convert old style modifiers, even if its just in your head, see advantage and disadvantage as +/-5.
Want to read deeper into the statistical analysis
We won’t go deep into the statistical analysis of rolling advantage in D&D#5E, but if you want to read those maths heavy topics you can read these two; Bob Carpenters article – Probabilities for Advantage and Disadvantage or Sterno’s question on RPG Stack Exchange.
Examples of RAW D&D5E advantages
Here are some examples of where advantage and disadvantage are applied, as mentioned in the PHB, MM or Dungeon Masters Guide:
The fighters ‘protection’
Training for years, the fighter not only knows how to inflict damage, but also how to shield friends from it.
If a creature within 5 foot of a fighter class character, an attacker suffers from disadvantage.
Protection falls under fighting style on page 72 of the Players Handbook
The ghasts ‘turning defiance’
The evil undead ghasts dwell in dark places of decay, feasting on decomposing flesh. You’re likely to smell a ghasts lair long before you’ve seen it.
If players were to cast spells to try and turn any undead creature within 30 foot of the ghast, their turning defiance feat grants all those fellow undead advantage.
The gnomes ‘stone camouflage’
Far below the surface of the world dwell the strong yet short race of the deep gnomes. With their pointy ears and bulging muscles, they’re at home amongst stone.
If they’re ever trying to hide or creep within rocky terrain, deep gnomes can use their stone camouflage to gain advantage to their stealth dexterity rolls.
Divination ‘foresight’ spell
For 8 hours, the spell of foresight grants the target immunity to being surprised, as well as advantage to all attack rolls, ability checks and saving throws.
If this wasn’t good enough, creatures fighting the target are at disadvantage for all their attacks.
Looking at how advantage and disadvantage affects the odds, that’s some powerful magic right there.
More can be read about the foresight spell on page 244 of the Players Handbook.
‘Dodging’ in combat
If a character shifts his focus in combat to be purely defensive, he forces any attacking creature to attack with disadvantage. At the same time, the dodging character gains advantage on all their dexterity saving throws.
More can be read about the dodge action on page 192 of the Players Handbook.
Now that you know what is advantage, you’re hopefully a master of dishing out advantage and disadvantage so read out top tips for new DMs.