Advantage and Disadvantage Calculator
See how advantage and disadvantage change your d20 success chance against a target number in tabletop RPGs.
Inputs
Results
Normal Roll
55 %
With Advantage
79.8 %
With Disadvantage
30.3 %
How it's calculated
On a d20 you succeed when the roll plus your modifier meets the DC — a natural roll of (DC − modifier) or higher — giving p = successful faces ÷ 20. Advantage (roll twice, keep the higher) = 1 − (1 − p)²; disadvantage (keep the lower) = p². Natural 1 and 20 auto-rules aren't applied.
Related calculators
- Drop Rate Calculator
Find your odds of getting a drop over many attempts, and how many tries it takes to be reasonably sure.
- DPS Calculator
Calculate damage per second from your hit damage, attack speed, and critical hit stats.
- eDPI Sensitivity Calculator
Find your effective DPI (eDPI) from your mouse DPI and in-game sensitivity to compare aim settings.
- Win Rate Calculator
Calculate your win rate from wins and losses, and how many wins in a row you need to reach a target.
- Nether Coordinate Calculator
Convert coordinates between the Overworld and the Nether to line up your portals (X and Z divide by 8).
- XP and Levels Calculator
Find the total experience points needed to go from your current level to a target level.