Dice notation
Tabletop games write rolls like 3d6+2: roll three six-sided dice and add 2. Set “Number of dice” to 3, die to d6 and modifier to 2. The average of one die is (sides + 1) ÷ 2, so 3d6 averages 10.5.
Advantage and disadvantage
In Dungeons & Dragons 5th edition, advantage means rolling two d20 and keeping the higher; disadvantage keeps the lower. Advantage raises the average d20 result from 10.5 to about 13.8.
Fairness
Physical dice can be slightly unbalanced. These use your browser’s secure random generator with rejection sampling, so every face has exactly the same chance.
Frequently asked questions
How do I roll a d100 (percentile)?
Pick d100 — you get a number from 1 to 100.
Can I roll with the keyboard?
Press Enter to roll again.
Last reviewed 2026-10-14.