Weighted Dice Roller
A fair die gives every face the same chance; a weighted one does not, and the interesting part is how hard that is to see. Set one face three times as likely as the others and a hundred rolls will often look unremarkable. This lets you set the weights, roll as many times as you like, and compare what the weights promised against what actually came up.
What this generator does
Turns the weights you set into a probability for each face, rolls that many times, and reports both the expected count and the count that actually came up for every face.
How to use this tool
- Set a weight for each face — a face weighted zero can never come up.
- Choose how many rolls to make.
- Compare the expected count against what actually appeared.
- Roll a hundred, then ten thousand, and watch the drift shrink.
Understanding the controls
- Weight for each face
- Any non-negative numbers — they need not add to anything, since only their proportions matter. A weight of zero makes that face impossible.
- How many rolls
- Up to a hundred thousand. Drift falls with the square root of this, so ten thousand rolls is only ten times sharper than a hundred.
- Seed
- A word reproduces exactly the same run, which is useful for showing the same example twice.
Common use cases
- Modelling a die that is not fair, for a game or a demonstration
- Seeing how many rolls it takes before bias becomes obvious
- Producing draws with a chosen distribution
- Teaching that a small sample proves very little
- Testing a scoring rule against a deliberately skewed die
How this generator works
The face is chosen by a single whole-number draw against cumulative weights, so no rounding decides an outcome. Afterwards, the counts are checked to add up to the number of rolls, the probabilities to add up to one, and — the sharpest check — any face weighted zero is confirmed never to have appeared.
Randomness and fairness
Draws come from the browser's secure generator, biased by the weights you set. A seed reproduces the same run exactly — that path is deterministic, not cryptographic, and exists so an example can be shown twice.
For how randomness is produced across the whole site, see how Generate Random works.
Limitations and good to know
- Up to twenty faces, which covers ordinary dice and most custom ones.
- The rolls are independent, so this models a loaded die rather than one that wears or sticks.
- Only the first two hundred rolls are listed individually; the counts cover them all.
- The comparison is descriptive — no statistical test is run, and a difference that looks large may be ordinary.
- Weightings are not remembered, so a die you have tuned needs its seed writing down.
Privacy and your data
Weights and rolls stay in your browser. Nothing is transmitted or stored.
Related generators
- Five-Dice Hold OptimiserWhich of your five dice to keep, worked out over every outcome of every choice rather than guessed.
- Push-Your-Luck Stopping CalculatorThe pot at which rolling again stops paying, worked out exactly for any die and any busting face.
- Dice Countdown RollerRolls six dice, sets one aside, rolls the rest — the whole countdown to a single die, laid out as a sheet.
- Dice Fairness TestRuns a chi-square test on your recorded rolls and is clear that failing to find bias is not the same as proving fairness.