A “loaded” die is one whose centre of mass isn’t at its centre, so it tends to settle with the heavy side down and a favoured number up. Deliberate loading — hidden weights, off-centre cavities — is rare outside stage magic. Far more common is honest manufacturing bias: air bubbles, uneven material, deep hollow pips and rounded edges that nudge a cheap die away from true. Either way, the same tests catch it.
The salt-water float test
This is the classic check, and it works because a fair die’s balance point sits dead centre.
- Dissolve several tablespoons of salt into a glass of warm water — keep stirring until the water is dense enough to float the die.
- Drop the die in and give it a gentle spin with your finger.
- Watch which face turns upward. A fair die will stop in random orientations each time you nudge it. A biased die will keep rotating to bring the same heavy face down and the same number up.
Repeat the nudge a dozen times. If one number surfaces again and again, the die’s weight is off. This test targets casino-style dice especially well; heavily inked or numbered dice have their own tiny imbalances from the paint alone, so read the result as a strong tendency rather than a single reading.
The spin test
A quicker, drier cousin of the float test: stand the die on a corner or spin it like a top on a hard, smooth surface. A well-balanced die spins cleanly and topples in no particular direction. One with an off-centre mass wobbles and consistently falls the same way. It is less sensitive than the float test but needs nothing but a flat table.
Inspect the edges and corners
Before any water, just look closely.
| Feature | What it tells you |
|---|---|
| Rounded vs sharp edges | Rounded edges (common on cheap dice) make some faces easier to roll off; casino dice have razor-sharp edges for exactly this reason. |
| Hollow painted pips | Drilled pips remove material unevenly — the 6-face loses more than the 1-face. Casino dice fill the pips with equal-density paint to compensate. |
| Bubbles or cloudiness | Trapped air inside translucent dice shifts the centre of mass off true. |
| Uneven faces or seams | Visible moulding flash or a face that isn’t flat means the die won’t sit or roll symmetrically. |
The chi-squared “roll 100 times” test
The float test finds imbalance; a rolling test finds actual bias in play. Roll the die many times — a hundred is a reasonable minimum, more is better — and tally how often each face appears. For a fair d6 rolled 120 times you’d expect 20 of each face, but you will never get exactly that: real randomness always scatters around the expectation. The question is whether the scatter is bigger than chance allows.
The chi-squared test answers this. For each face, take (observed − expected), square it, divide by the expected count, and add up the results across all faces. A small total means the die looks fair; a large total means the results stray further from even than luck comfortably explains, and the die is probably biased. You don’t need to memorise the threshold — the point is that one or two unusual faces prove nothing, but a persistent lean across a big sample is real evidence. The bigger your sample, the more confident the verdict.
Casino precision vs cheap dice
The reason casinos machine their dice to tight tolerances — sharp edges, flush pips filled with equal-density material, transparent bodies to reveal hidden weights, often serial-numbered — is that ordinary dice are measurably imperfect. A typical hobby die is fine for a friendly game and its bias is usually too small to notice roll to roll, but it is not the same object as a precision die. If fairness genuinely matters to you, that gap is the whole reason these tests exist.
If you’d rather skip the salt water entirely, a good digital roller has no mass to go off-centre — you can roll dice that stay perfectly balanced every time. (More on why in are digital dice fair?)
Try it yourself. Dice Drop rolls real physics dice in your browser — pools, exploding dice and modifiers built in.
🎲 Roll dice freeKeep reading: how RNG makes digital dice fair, or a short history of dice.