Advantage & Disadvantage, Explained
The simplest good rule in modern d20 games — and the math behind it.
Advantage and disadvantage are the d20 game's elegant way of saying "this is easier" or "this is harder" without fiddly bonuses. The rule is tiny: roll two d20s instead of one. With advantage, keep the higher die. With disadvantage, keep the lower. That's the whole thing — and you can do it in one tap on the dice roller.
When do you get it?
The GM grants advantage when circumstances clearly favor you: attacking a surprised enemy, helping an ally, the right tool for the job. Disadvantage comes from anything that hinders you: attacking in the dark, firing at long range, acting while poisoned or frightened. You don't add a number — you just change how the die is rolled.
The math: it's worth about +5 (or −5)
Rolling two dice and keeping the higher pulls your average result up noticeably. On a flat d20 your average roll is 10.5; with advantage it jumps to about 13.8, and with disadvantage it drops to about 7.2. In rough terms, advantage is worth around +5 to your roll near the middle of the range, where most checks are decided. It also makes a natural 20 far more likely — almost double the chance — and a natural 1 far rarer.
Two rules people forget
- It doesn't stack. Three sources of advantage still means roll two dice, keep the higher. You never roll three and keep the best.
- They cancel out. If you have advantage and disadvantage at the same time, they cancel completely — you roll one normal d20, no matter how many of each you have.
Rolling it without the headache
Tracking two physical dice and remembering which to keep is exactly the kind of thing that slows combat down. Set the dice roller to Advantage or Disadvantage and tap d20 — it rolls both, keeps the right one, and crosses out the die you dropped so the table can see it was fair.
- Does advantage apply to damage?
- No. Advantage and disadvantage only affect a single d20 roll — an attack, a check or a save. Damage pools like 2d6 are rolled normally.
- What if I have advantage from two things?
- Still just two dice, keep the higher. Multiple sources don't add up.
- What happens with both advantage and disadvantage?
- They cancel out entirely and you roll a single normal d20.