Dice Roller

Roll RPG dice online with d4 to d100, expressions like 3d6+2, and d20 advantage or disadvantage, drawn from your browser's crypto random source.

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Range 5 to 20 · average 12.5

Enter dice notation above and roll.

d20 with advantage / disadvantage

D&D 5e: advantage rolls two d20 and keeps the higher; disadvantage keeps the lower.

Accepts up to 100 dice per roll, up to d1000.

🔒 Private by design: everything runs locally in your browser and never uploaded to any server.

Written and maintained by Last updated

The notation this parser actually accepts

The grammar is small and strict, which is a feature. An expression is a sequence of terms joined by plus or minus signs, where a term is either a dice group or a plain number. A dice group is NdM, and the count is optional, so d20 means 1d20. Whitespace is stripped and case is ignored, so 3D6 + 2 and 3d6+2 parse identically.

You can chain as many terms as you like. 2d6+1d8+3 rolls two six-sided dice, one eight-sided die, and adds three. A group can be subtracted too: 2d6-1d4 rolls both groups and takes the d4 total away, which is why that expression can legitimately land on a negative number. Its real range is -2 to 11.

What the grammar deliberately does not do is guess. Two dice groups written next to each other with no operator, as in d20d20, is an error rather than two rolls, because silently inferring an operator is how a roller ends up producing a number the player never asked for. The same goes for 3d, d0, 0d6 and a dangling 3d6+.

Where the numbers come from

Every die face is drawn by the same randomInt helper the Random Number Generator uses, imported directly rather than reimplemented. It pulls a 32-bit unsigned word from crypto.getRandomValues and then rejects any value at or above the largest exact multiple of the die size that fits in 32 bits, redrawing until it gets one below the cut.

That rejection step is the whole point. Taking a raw 32-bit value modulo 20 would make the low faces very slightly more likely than the high ones, because 2^32 is not divisible by 20. Discarding the overhang removes that skew entirely, so a natural 20 really is a one in twenty event. The same primitive is shared by the Coin Flip and the Wheel of Names, which is why all three can make the same fairness claim.

Rolling an expression and reading what comes back

  1. Type into the Dice notation box, or tap one of the preset chips from d4 through d100. Tapping a chip replaces whatever was in the box rather than appending to it.
  2. Glance at the line underneath, which reports the range and average for what you have typed. For 3d6+2 it reads a range of 5 to 20 and an average of 12.5.
  3. Click Roll dice, or just press Enter in the box.
  4. Read the large total, then the breakdown below it, which lists each group’s individual faces and the modifier as a separate row. Faces at the maximum and at 1 are styled differently so criticals stand out.

The total is always the signed sum of the faces shown plus the modifier, with nothing hidden: a group written with a minus is labelled with one and subtracted, which is the point of printing every die rather than just the sum.

Advantage and disadvantage, scoped to the d20

The second panel implements the D&D 5e rule literally. Advantage rolls two twenty-sided dice and keeps the higher, disadvantage rolls two and keeps the lower, and Normal rolls a single d20. Whatever you put in the Modifier field is added to the kept die, not to both.

Both dice are always displayed, with the kept one marked and the discarded one visibly dropped, so you can see the roll that was thrown away. This is a separate control from the expression box on purpose: the 5e rule is defined for the d20 and nothing else, and dressing it up as generic notation would imply support the parser does not have.

Range and average, before you commit to a roll

The stats line is computed exactly, not sampled. For a positive group NdM the minimum is N, the maximum is N*M, and the mean is N*(M+1)/2, all shifted by the flat modifier. Subtracted groups contribute their extremes flipped and everything adds up linearly.

It is genuinely useful for sanity-checking a homebrew expression before you roll it. 2d6+1d8+3 runs from 6 to 23 with a mean of 14.5. 4d6 runs 4 to 24 with a mean of 14. 100d6 runs 100 to 600 with a mean of 350. If a number in that line surprises you, the expression is probably not the one you meant to type.

Errors, caps and the history list

Bad input produces a specific message, never a fabricated result. Typing 0d6 says each dice group must roll at least one die. Typing d0 says a die must have between 1 and 1000 sides. Typing d20d20 tells you to separate dice with a plus or minus. Exceeding one hundred dice is refused outright. An empty box shows nothing at all and simply leaves the roll button disabled, which is deliberate: an empty box is not a mistake, it is just not a roll yet.

Every completed roll is appended to a history list capped at twenty entries, formatted as the expression, the faces and the total, for example 3d6+2: 3d6 [4, 1, 6] + 2 = 13. It is held in memory for the current tab only, and a Clear button wipes it early. For picking who goes first rather than what they rolled, the Tournament Bracket Generator and the rest of the generators cover the surrounding table logistics.

See it in action

Screenshot of the Dice Roller tool with dice buttons for the standard polyhedral set, a roll area showing each die face and the total, and an advanced field for notation like 2d6+3
Dice Roller mid-process: dice buttons for the standard polyhedral set, a roll area showing each die face and the total, and an advanced field for notation like 2d6+3.
Diagram: where the work happens on a SysFenix page that has no file input at all: the tool arrives as ordinary JavaScript inside the page, works the answer out on your own device and renders it in place, so the upload, queue and server-side record a typical online tool needs never happen
Where the work happens on a SysFenix page that has no file input at all: the tool arrives as ordinary JavaScript inside the page, works the answer out on your own device and renders it in place, so the upload, queue and server-side record a typical online tool needs never happen.

Frequently asked questions

What is the largest roll this will accept?

One hundred dice across the whole expression, and up to 1000 faces on any single die. So 100d6 is fine, 1d1000 is fine, and 101d6 is refused with a message rather than silently truncated. The line under the widget states both caps.

Can I write keep-highest notation like 4d6kh3?

No. The grammar understands dice groups, flat constants and plus or minus signs, and nothing else, so there is no keep, drop, reroll or exploding syntax. For classic stat generation, roll 4d6 and discard the lowest die yourself from the list of individual faces the tool prints. The one keep rule that is built in is d20 advantage and disadvantage, which has its own section.

What random source draws the faces?

Each face comes from crypto.getRandomValues on a 32-bit word, filtered through rejection sampling so no face is even slightly favored. Values at or above the largest exact multiple of the die size that fits in 32 bits are discarded and redrawn, which is what removes the modulo bias a plain remainder would introduce. The same helper backs the coin flip and name wheel tools on this site.

Is the number flickering during the animation the real roll?

No, and that distinction matters. The actual result is computed once, before the animation starts, from the crypto source described above. The digits churning for those few hundred milliseconds are cosmetic filler drawn with ordinary Math.random, and they are thrown away the moment the real value is revealed.

Why does the roll button do nothing when the box is empty?

An empty box is not a parse failure, it is just nothing to roll, so the button disables itself instead of showing an error. Errors appear only once you have typed something the grammar cannot consume, such as 0d6 or a trailing plus sign. In both cases the tool refuses to produce a number rather than inventing one.

How long does the roll history keep going?

It holds the twenty most recent entries, newest first, and each line records the expression, every individual die face and the final total so you can audit any roll after the fact. A Clear button empties it on demand. The list lives only in the current tab and disappears on reload.

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