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.

Dice Roller — Gera Tools

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 & Dragons.

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 1-20 exactly the same chance. The individual rolls are summed, then the modifier is added (or subtracted) to give the total.

Example

Rolling 2d6+3 (two six-sided dice plus 3):

rolls 4 and 5 → 4 + 5 = 9, + 3 modifier = 12 total

Notation	Meaning	Range
1d20	one twenty-sided die	1–20
2d6+3	two d6 plus 3	5–15
4d4	four four-sided dice	4–16
1d100	percentile die	1–100

You see each individual result plus the combined total. Everything runs in your browser — nothing is uploaded.