Decision tool

Dice Roller

Any number of dice, any number of sides. Roll one, or roll ten thousand and see whether the spread is fair.

Total

—

Dice Sides

Test with rolls

This session's rolls (clears when you close the tab)

How this dice roller works

Each die is drawn from crypto.getRandomValues(), the generator built into your browser by the Web Crypto API and seeded by your operating system from hardware entropy. A number is drawn from the full 32-bit range and reduced to your die's faces by rejection sampling, so no face is even slightly more likely than another. Reducing with a plain modulo would bias the low faces, and on a die with an awkward number of sides that bias is measurable.

Nothing is drawn on a server. The dice are rolled on your device, so the results cannot be seen, logged or influenced by anyone else.

Rolling different dice

Set the number of dice and the number of sides, then press Roll. Any combination from 1d2 to 1000d1000 is allowed, which covers everything from role-playing dice to picking a random number out of a range.

The quick buttons fill in common cases: d6 is the standard die, d20 is what tabletop games use, d100 gives you a clean percentage, and 2d6 is the classic bell-curve roll. With two dice the totals cluster around seven, and a single seven is more likely than a two — which surprises people the first time they see it.

What the distribution check does

One roll tells you almost nothing. Tens of thousands of rolls tell you whether the dice are fair, and that is what Check distribution is for: it rolls your chosen die many times and compares how often each face came up against what an even spread would predict.

It then runs a chi-square test on the result. If the dice were biased, the counts would differ from expectation in a way that happens by chance less than 5% of the time, and the test says so. A passing result is not proof of fairness — a rigged die passes about 19 times out of 20 — but a failing result is a strong signal that something is wrong, which is the direction that matters.

You will occasionally get a warning on a perfectly honest die. That is what a 5% threshold means, and it is exactly the same behaviour a real die shows. Run it again with a different number of rolls.

Odds on more than one die

With two dice the outcomes are not equally likely. For 2d6 the totals run from 2 to 12, but they are not all the same: there is only one way to roll a 2 and six ways to roll a 7, so the middle of the range is seven times more likely than the edges. Three dice stretch this further, and the shape of the curve is why "roll for it" and "roll 3d6, keep the highest" produce very different games.

A useful shortcut: to pick a single number from 1 to N, roll one die with N sides rather than trying to combine dice. It is uniform by definition.

Coin Flip — the two-sided case, with its own fairness test
Wheel of Fortune — choose from a list you write yourself
Card Pull — draw from a shuffled deck
Randomness Check — test this site's generator directly

Privacy and terms