Roll a D20

Tap the die to roll a fair twenty sided die. Add your modifier, switch on advantage or disadvantage, and set a DC or AC to see your odds before you roll.

What rolling a d20 means

You roll one twenty sided die and add whatever modifier applies, like your attack bonus or a skill bonus. Then you compare the total to the target number. Each face from 1 to 20 has the same 5% chance on a fair die.

Odds of a natural 20

On a single d20 the chance of a natural 20 is 1 in 20, or 5%. With advantage you roll two dice and keep the higher, so the chance rises to 9.75% (1 minus 0.95 squared). With disadvantage it drops to 0.25% (0.05 squared). The same math applies to a natural 1 in reverse.

What a natural 20 does in 5e

On an attack roll, a natural 20 hits no matter the target's AC and counts as a critical hit, so you roll the damage dice twice. On a death saving throw, a natural 20 brings you back with 1 hit point. On ability checks and most saving throws, a 20 is just a high number unless your table plays a house rule.

Advantage in practice

Advantage helps most when you need a middling roll. If you need 11 or higher, a single d20 gives you 50%, and advantage raises that to 75%. Use the DC box above to check any number.