Dice Roller guide
Roll any combination of polyhedral dice for Dungeons & Dragons, Pathfinder, board games, or probability lessons. Type standard notation, use one-tap buttons for advantage and ability scores, and keep a running history.
Dice notation, decoded
Tabletop games write rolls as NdS: N dice with S sides. 3d8 is three eight-sided dice added together. A leading 1 is optional, so d20 and 1d20 mean the same thing. A modifier goes on the end with + or -: 1d20+5 is an attack roll with a +5 bonus. You can chain groups, so 1d8+2d6+4 rolls a d8 and two d6s and adds 4.
Two extensions cover most of what Dungeons & Dragons players need. kh (keep highest) and kl (keep lowest) roll a group and keep only some of the dice: 2d20kh1 keeps the higher of two d20s, and 4d6kh3 drops the lowest of four d6s. d% is shorthand for d100. The roller accepts all of these and shows each die, with dropped dice struck through.
The math behind every roll
A fair die with S sides averages (S + 1) ÷ 2. So a d4 averages 2.5, a d6 3.5, a d8 4.5, a d10 5.5, a d12 6.5, and a d20 10.5. Averages add, so N dice average N × (S + 1) ÷ 2. 8d6 averages 28, which is why a 3rd-level Fireball deals 28 damage on average.
The range runs from N (every die shows 1) to N × S (every die shows its max), plus the modifier. The roller prints that range with every result, which helps when a DM asks whether a number is even possible.
More dice means results bunch toward the middle. One d12 is flat: every number from 1 to 12 is equally likely. 2d6 has the same 2 to 12 range, but 7 comes up 6 times in 36 (16.7%) while 2 and 12 come up once in 36 each (2.8%). That bell shape is why Catan's 6 and 8 tiles are the most valuable.
Worked example: advantage and ability scores
Advantage in D&D 5e means rolling two d20s and keeping the higher. Averaged over all 400 combinations, that is 13.83, more than three points better than a single d20. Needing a 15 or higher, one d20 succeeds 30% of the time; with advantage, 51%. Disadvantage mirrors it: 7.18 average.
Rolling ability scores with 4d6-drop-lowest averages 12.24 per score, versus 10.5 for straight 3d6. Across six abilities that is roughly 10 extra points, which is why most tables prefer it. Tap the Stat button six times and read the history list to fill in a character sheet.
Is a digital dice roller fair?
This roller draws numbers from crypto.getRandomValues, the browser's cryptographically secure generator, the same source used to create encryption keys. Every face has an equal chance, and past rolls do not influence future ones.
Physical dice are not always so fair. Cheap acrylic dice have drilled pips and uneven density, and tests with saltwater float checks routinely find d20s that favor certain faces. That does not make physical dice bad; it just means a streak of ones on a screen is ordinary randomness, not a broken roller. Streaks happen: the chance of rolling at least one natural 1 in 20 d20 rolls is 64%.
Common mistakes
Adding the modifier once per die. 2d6+3 adds 3 to the total, not to each die. If a rule adds a bonus per die, write it out, such as 2d6+6.
Doubling the modifier on a critical hit. In 5e, a crit doubles the dice, not the modifier: a longsword crit with +3 Strength is 2d8+3, not 2d8+6.
Confusing advantage with rolling twice and adding. Advantage keeps one die. 2d20 without kh1 adds both dice, giving a 2 to 40 range that no D&D rule uses.
Beyond D&D
The same notation covers most board and tabletop games: 2d6 for Monopoly and Catan, 3d6 for GURPS, d10 pools for World of Darkness, and d100 for Call of Cthulhu skill checks. Teachers use it for probability lessons, since rolling 2d6 fifty times and tallying the history makes the bell curve visible. For a simple yes or no, the coin flip tool is faster, and for a number in a custom range, use the random number generator.
Frequently asked questions
How do I read dice notation like 2d6+3?
The number before d is how many dice, the number after is how many sides, and anything after + or - is a modifier. 2d6+3 means roll two six-sided dice, add them, then add 3, for a result between 5 and 15.
How do I roll with advantage in D&D 5e?
Roll two d20s and keep the higher one. Tap Advantage or type 2d20kh1 (keep highest 1). Disadvantage is 2d20kl1. Advantage raises the average d20 result from 10.5 to about 13.8.
How do I roll stats with 4d6 drop the lowest?
Tap "Stat (4d6 drop lowest)" or type 4d6kh3. The dropped die is shown struck through. Roll it six times for a full array; the average result is about 12.24 per ability score.
Is this dice roller truly random?
It uses the browser's cryptographic random number generator (crypto.getRandomValues), which passes statistical randomness tests. Cheap physical dice are often measurably biased because of uneven drilling and rounded edges.
What is the average roll of a die?
For one fair die, (sides + 1) / 2. A d6 averages 3.5, a d20 averages 10.5, and 8d6 (a Fireball) averages 28.
Can I roll different dice at once?
Yes. Chain terms with + or -, such as 1d8+2d6+4 for a sneak attack. Each group is shown separately, along with the minimum and maximum possible total.
What does d% or d100 mean?
A percentile roll from 1 to 100. At the table it is usually two d10s, one for tens and one for ones. Type d% or 1d100.
Does the dice roller run privately in my browser?
Everything runs in your browser. Nothing you enter is uploaded to a server or stored by us.