Dice Roller

What it does

Type any dice expression in NdM notation — like 2d6, 4d20 or 3d6+2 — and the tool rolls that combination in your browser. Each die is shown separately so you can see the individual results, along with the sum and the total after any modifier. Press Reroll for a fresh set.

How it works

NdM+K means "roll N dice with M sides each, then add K." The expression is parsed with the pattern NdM optionally followed by +K or −K. The tool accepts 1–100 dice with 2–1000 sides and a modifier between −1000 and +1000 — enough for D&D, most tabletop systems and quick classroom probability demos.

Each die is rolled independently by drawing a uniform whole number in the range 1–M. The randomness comes from crypto.getRandomValues, the browser's cryptographically secure generator, not Math.random. To keep every face equally likely, the code uses rejection sampling: it discards the rare random values that would otherwise bias the result (the "modulo bias") and draws again. The sum is the total of the raw rolls; the total is the sum plus the modifier.

Worked example

Roll 2d6 — 2 six-sided dice with no modifier. Parsing gives count = 2, sides = 6, modifier = 0. Each die lands somewhere between 1 and 6, so the total falls between 2 and 12, with an expected average of 7.

A possible outcome: the first die shows a 4, the second shows a 3 — sum 7, total 7. Your own roll will vary; that's the point. Reload the widget and you will see a different pair almost every time.

Dice notation and the standard dice

Every entry above — 1d4, 2d6, 1d20 — follows the same grammar: NdM+K. N is how many dice you're rolling. M is the number of sides on each one. +K (or −K) is a flat modifier applied once to the total, not to every die. Leave N off in your head and d20 just means "one twenty-sided die"; the tool still needs the explicit 1, so type 1d20.

The seven dice below are the polyhedra you'll find in a standard tabletop set. Every game that uses NdM notation — Dungeons & Dragons, Pathfinder, Call of Cthulhu, Shadowrun, Warhammer — is built on some combination of these.

1d4 — the tetrahedron

Four triangular faces; it looks like a small pyramid and famously refuses to lie flat on a tilted table. In D&D it's the damage die for the smallest weapons (dagger, sling) and for magic missile. Because there's no top face, the number rolled is usually read from the upright corner — a habit that catches out new players every time.

1d6 — the cube

The die you grew up with: six pipped faces, opposite sides always summing to seven. It's the workhorse of board games, most Warhammer rolls, and D&D damage dice like 1d6 (shortsword) and 8d6 (fireball). Its flat probability curve is why 2d6 is a staple of probability lessons — roll a pair enough times and the sums cluster around 7 in a clean triangular distribution.

1d8 — the octahedron

Eight triangular faces meeting at points top and bottom. It's the middle-weight damage die in D&D: 1d8 for a longsword, 1d8 for cleric healing, 1d8 per level for a fighter's hit points. Rolls smoothly; less prone than the d4 to “chandelier” landings.

1d10 — the pentagonal trapezohedron

Ten kite-shaped faces. Two forms come in a standard set: one numbered 1–10 (or 0–9, treated as 10) for straight 1d10 rolls, and a percentile version marked 00, 10, 20…90 that pairs with the units d10 to make a d100 roll. The Storyteller/Storypath systems (Vampire: The Masquerade, Exalted) build their whole dice-pool mechanic on d10s.

1d12 — the dodecahedron

Twelve pentagonal faces — the classical Platonic solid Plato associated with the cosmos. In modern D&D it's the barbarian's greataxe and the dragonborn's breath weapon, but it's genuinely the least-used die in the set. Rolling one always feels like an event.

1d20 — the icosahedron

Twenty triangular faces — the signature D&D die. Every attack roll, saving throw, ability check and skill check in fifth edition is a 1d20 plus modifiers, compared against a target number. Rolling a natural 20 is a critical hit; a natural 1 is a critical fumble. If you own one polyhedron, this is the one.

1d100 — the percentile roll

Not always a real hundred-sided die (the "zocchihedron" exists but rolls forever); in practice 1d100 is two d10s read as tens and units, giving a flat 1–100. It's the backbone of Call of Cthulhu's skill checks, Warhammer Fantasy Roleplay's combat, and any random-encounter table that needs fine granularity. Some systems treat 00 + 0 as 100; others as zero — check the rulebook.

Anything outside this list — 1d3, 1d30, 1d1000 — is fair game in the tool but you probably won't find the physical die in a game shop. Roll it here instead.

Common uses

• D&D and tabletop RPGs. Attack rolls (1d20+5), damage (2d6+3), fireball damage (8d6) — the notation is standard across every fifth-edition-style game.
• Board games with missing dice. When the physical die from the box has gone missing under the sofa, roll 1d6 here instead. Also handy for percentile checks in games that use 1d100.
• Teaching probability. Roll 2d6 a few dozen times and watch the sums cluster around 7 — a quick, tangible demonstration of why rolling two dice is nothing like rolling one.
• Deciding between options. Two choices? 1d2. Four? 1d4. Fair, fast, no coins needed.

Frequently asked

Is this cryptographically random?

Yes. Each roll is drawn from crypto.getRandomValues using rejection sampling to prevent the modulo bias that a naïve random % sides would introduce. The outcomes are unbiased and unpredictable — good enough for a security context, and comfortably better than needed for a game.

How many dice can I roll at once?

Up to 100 dice in a single expression. That covers every practical tabletop combination (8d6 for fireball, 10d10 for a Shadowrun test, and so on) without letting the page grind on runaway inputs.

What's the highest-sided die you support?

Up to d1000. Everything from a coin flip (1d2) through the standard tabletop polyhedra (d4, d6, d8, d10, d12, d20) and the percentile die (1d100) is well within range.

Does the modifier apply once, or to every die?

Once — added to the sum at the end, matching the tabletop convention. 3d6+2 rolls three six-sided dice and adds two to the total, not two to each die.

Can I keep the highest die or drop the lowest?

Not in this first version. NdM+K is deliberately simple so the tool stays predictable. Advantage-style mechanics (4d6 drop the lowest, 2d20 keep the highest) are on the roadmap.

Do you record what I roll?

No. Every roll happens in your browser in JavaScript; nothing is sent to ToolHare or stored between visits.

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