Which dice can I roll?

You can roll any number of d4, d6, d8, d10, d12, d20 or d100 dice, plus an optional modifier added to the total — covering most tabletop and RPG needs.

What does a notation like 2d6+3 mean?

It means roll two six-sided dice and add a modifier of 3 to the total. Set the dice type to d6, the count to 2 and the modifier to 3, then roll — the tool shows each die and the final total including the modifier.

Yes. Each die uses the browser's Web Crypto API with modulo bias removed, so every face is equally likely on every roll.

How does removing modulo bias work?

A raw random 32-bit value mapped onto, say, 1-20 with a plain modulo would slightly favour the lower faces. The roller discards values in the small leftover range and re-draws, so every face has exactly equal probability.

Can I roll many dice at once?

Yes — you can roll from 1 up to 100 dice in a single click. Each die is rolled independently and the results are summed, then any modifier is added to give the total.

Can the modifier be negative?

Yes. Enter a negative modifier to subtract from the total, for example a penalty on a skill check. The tool shows whether the modifier is added or subtracted in the breakdown.

Is my roll data shared anywhere?

No — all rolling happens locally in your browser using the Web Crypto API. Nothing is uploaded or recorded.

What is the Dice Roller?

Free online dice roller for d4, d6, d8, d10, d12, d20 and d100 with custom dice counts and modifiers. Uses the Web Crypto API for fair rolls and runs entirely in your browser — nothing is uploaded. It runs free in your browser on Gera Tools, with nothing uploaded.

Dice Roller — Gera Tools

Name: Dice Roller
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

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Dice roller

Roll any combination of standard polyhedral dice — d4, d6, d8, d10, d12, d20 and d100 — with an optional modifier for skill checks, attack rolls and board games. It is a fast stand-in for physical dice for tabletop RPGs like Dungeons and Dragons, Pathfinder, Call of Cthulhu, and any other system using polyhedral dice.

How it works

Pick the die type, how many to roll (1 to 100) and an optional modifier. Each die is rolled using the browser’s Web Crypto API (crypto.getRandomValues), a cryptographically secure source. To keep every face equally likely, the roller uses rejection sampling: it discards any raw random value that would introduce modulo bias and re-draws, so a d20 gives each of 1 through 20 exactly the same chance. The individual rolls are summed, then the modifier is added (or subtracted) to give the total.

Understanding dice notation

Standard dice notation uses the form NdX+M — N dice of type X with optional modifier M.

Notation	Meaning	Result range
1d20	one twenty-sided die	1–20
2d6+3	two six-sided dice plus 3	5–15
4d4	four four-sided dice, no modifier	4–16
3d8−2	three eight-sided dice minus 2	1–22
1d100	percentile die (d100)	1–100

A negative modifier works the same way — it subtracts from the total, useful for disadvantage penalties in systems that use them.

When to use which die

Different RPG systems associate specific dice with different rolls:

d4 — low-damage weapons (daggers, magic missiles in some editions), some healing potions
d6 — standard damage die for many weapons, also used in board games
d8 — longswords and mid-tier weapons; Hit Dice for Clerics in D&D
d10 — heavy weapons, percentile rolls (paired d10s for d100), some class hit dice
d12 — greataxes and barbarian Hit Dice in D&D; less common but distinctive
d20 — the defining die of D&D-family games, used for attacks, saving throws, ability checks
d100 — skill checks in percentile systems like Call of Cthulhu and some editions of Warhammer RPG

Worked example

Rolling 2d6+3 for a rogue’s sneak attack: the two d6 land on 4 and 5, totalling 9, plus the +3 modifier gives 12 total. You see each die individually so you can verify the breakdown, not just trust the sum.

All rolling happens in your browser using the Web Crypto API. Nothing is uploaded or logged.