Rolling the Dice: A Beginner’s Guide to Understanding Advantage and Disadvantage in D&D

Dungeons and Dragons 5th edition introduced players to a new game mechanic, the concept of advantage and disadvantage. But what exactly does advantage and disadvantage mean, and how does it impact your character’s abilities and odds of success? Whether you’re a seasoned veteran or a newcomer to the world of D&D, it’s important to understand how this system works.
Advantage and disadvantage can have a profound effect on a wide range of elements within the game, from divine spells and monstrous creatures to player classes and skill checks. Understanding the ins and outs of this mechanic is crucial for players looking to make the most of their characters and improve their odds of success in every encounter.

What is advantage and disadvantage?

Advantage in D&D is one of the most exciting mechanics in the game. It allows you to roll two D20s instead of just one, giving you a greater chance of success in your ability checks and attack rolls. When you have advantage, you get to choose the highest roll from the two dice, giving you a better chance to achieve your desired outcome. It’s the perfect way to add an extra layer of excitement to the game, as you strive for success against the odds.

Disadvantage, on the other hand, is the polar opposite of advantage. Instead of rolling two D20s and selecting the highest, you’ll be rolling two and selecting the lowest. This can greatly impact your chances of success, but it also adds an extra level of challenge to the game. Whether you’re facing off against a powerful monster or attempting a difficult skill check, disadvantage can put the pressure on and make the outcome all the more thrilling.

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.

Dopplegangers get advantage in DnD5E

Dopplegangers get advantage in DnD5E (Pic from Forgotten Realms)

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

At ninth level, a druid may cast the powerful spell of foresight.

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.

Further Reading

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.

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