By EpicWinDND Editorial
Of all the rules in D&D 5th edition, advantage and disadvantage might be the most loved — and the most misunderstood. People know it means "roll twice," but they are fuzzy on which die to keep, whether it stacks, and how much of an edge it really gives. The good news is that it is one of the cleanest mechanics in the game. This guide walks through exactly how advantage and disadvantage work, the one rule that keeps them from snowballing, and what the probability actually looks like, so you know when the extra die matters and when it barely moves the needle.
The basic rule: roll two d20, keep one
Whenever something gives you advantage, you roll two twenty-sided dice instead of one and use the higher result. Disadvantage is the exact mirror: roll two and use the lower. That is the whole mechanic. It applies to the three things you roll a d20 for — attack rolls, ability checks, and saving throws — and it never changes the target number you are trying to beat. You still add your usual modifiers to whichever die you keep, then compare the total to the Armor Class or Difficulty Class as normal. The only difference is that you got to pick the friendlier of two rolls.
The one rule that keeps it simple: it never stacks
This is the part that trips people up. In 5e you can never have "double advantage." No matter how many things are working in your favor, you still roll just two dice and keep the higher — a second or third source of advantage adds nothing mechanically. More importantly, advantage and disadvantage cancel each other out completely. If even one circumstance gives you advantage and even one imposes disadvantage, the two neutralize and you roll a single, normal d20. It does not matter if you have three sources of advantage and only one of disadvantage; the moment both are present, you are back to one die. That binary design is deliberate: it keeps a fast-moving table from stopping to tally bonuses, because the answer is always either "roll one" or "roll two and keep one."
Where advantage and disadvantage come from
Plenty of situations grant or impose it. Helping an ally with the Help action gives them advantage on their next relevant roll; attacking a creature that cannot see you, or one that is prone (in melee), is a classic source of advantage. On the other side, the poisoned condition imposes disadvantage on attack rolls and ability checks, attacking a target at long range gives disadvantage, and trying to act while frightened of a visible threat does too. You do not need to memorize the full list — spells, class features, conditions, and the environment all feed into the same two words, which is exactly why the mechanic scales so gracefully. When the fiction says you have the upper hand, you get advantage; when it says you are compromised, you get disadvantage.
How much does it actually change your odds?
Here is where the flat d20 makes the math friendly. A single d20 has an average result of 10.5. The higher of two d20 averages 13.825, and the lower averages 7.175 — so as a rough rule of thumb, advantage is worth about +3.3 to your roll and disadvantage about −3.3. But that average hides the most useful fact: the size of the boost depends entirely on what you need to roll.
| How you roll | What you keep | Average d20 result | Effect vs a normal roll |
|---|---|---|---|
| Normal | Your one d20 | 10.5 | Baseline |
| Advantage | The higher of two d20 | 13.825 | About +3.3 on average |
| Disadvantage | The lower of two d20 | 7.175 | About −3.3 on average |
Advantage helps the most when your odds are near a coin flip and the least when a roll is nearly automatic or nearly impossible. The table below shows the real numbers. Advantage gives the biggest swing — a full +25 percentage points — right around a 50/50 roll, and only a few points when you needed almost any result anyway or needed a near-miracle.
| You need (on a bare d20) | Normal chance | With advantage | Points gained |
|---|---|---|---|
| 5 or higher (easy) | 80% | 96% | +16 |
| 10 or higher (medium) | 55% | 79.75% | +24.75 |
| 11 or higher (a coin flip) | 50% | 75% | +25 (the peak) |
| 15 or higher (hard) | 30% | 51% | +21 |
| 20 (a natural 20) | 5% | 9.75% | +4.75 |
What this means at the table
Two practical takeaways fall out of those numbers. First, advantage is most precious on the rolls that are genuinely in doubt; spending a resource to gain advantage on a roll you were going to make 80% of the time is mostly wasted. Second, advantage roughly doubles your chance of a natural 20: with two dice your odds of landing at least one 20 rise from 5% to about 9.75%, which is why advantage feels so good on a high-stakes attack. Disadvantage is the same story in reverse — it bites hardest on the middling rolls and makes a natural 1 far more likely. Treat advantage as worth somewhere between a +3 and +5 bonus depending on the situation, and you will judge its value correctly almost every time.
Reading two d20 at speed
Because advantage means scanning two dice and grabbing the higher number fast, a legible, high-contrast set earns its keep. A warm tiger's eye set ($59.99) or a sharp-edged silver-gray diamond-cut set ($79.99) makes "which of these two is higher?" a half-second glance instead of a squint. To be clear, no set rolls better — any fair die gives identical odds, and advantage comes from the rule, not the dice. You are just buying a d20 that reads instantly when you have two of them on the table. Browse the range in the gemstone dice collection.
Frequently Asked Questions
How do advantage and disadvantage work in D&D 5e?
When you have advantage you roll two d20 and use the higher result; with disadvantage you roll two and use the lower. You add your normal modifiers to whichever die you keep and compare it to the target number as usual. It applies to attack rolls, ability checks, and saving throws, and you only ever roll one extra die no matter how many sources you have.
Does advantage stack in 5e?
No. Having two or more sources of advantage is the same as having one — you still roll just two d20 and keep the higher. There is no 'double advantage' that lets you roll three dice. The benefit is binary: you either have advantage or you don't.
What happens if I have both advantage and disadvantage?
They cancel out completely. If even one circumstance gives advantage and even one imposes disadvantage, you have neither and roll a single normal d20. This is true even if you have several sources of one and only a single source of the other — the moment both are present, you are back to one die.
How much does advantage actually help?
On average it raises your roll by about +3.3 (the higher of two d20 averages 13.825 versus 10.5 for one). But the real benefit depends on the target: it peaks at about +25 percentage points on a 50/50 roll and is only a few points when a roll was nearly automatic or nearly impossible. A good rule of thumb is that advantage is worth roughly a +3 to +5 bonus.
Does advantage make a natural 20 more likely?
Yes. With one d20 your chance of a natural 20 is 5%. With advantage you roll two, so your chance of at least one 20 rises to about 9.75% — close to double. Disadvantage works the same way in reverse, making a natural 1 far more likely.
Do better dice change my advantage odds?
No. Any fair, well-made die gives the same odds regardless of material, color, or price. Advantage comes entirely from the rule — rolling two dice and keeping one — not from the set. A nicer set just reads faster when you have two d20 on the table, which is genuinely handy, but it does not change the math.