Dice guide / Published July 15, 2026

Are My Dice Fair? How to Test Dice Balance

What does a "fair" die actually mean?

A fair die is one where every face has an equal chance of landing up. For a six-sided die that is a 1-in-6 chance per face; for a D20, 1-in-20. In practice no physical die is perfect, but a well-made die is close enough that any bias is too small to notice in play. Fairness comes down to three things: even internal density (no heavy or hollow spots), accurate face geometry (flat, correctly sized faces), and consistent manufacturing. When one of those slips, a die can develop a measurable bias.

How to test dice balance: the salt water float test

The salt water test is the classic at-home method for plastic (acrylic and resin) dice. It works by making the water dense enough that the die floats, so any internal imbalance shows up as the die consistently turning its lighter side upward.

1. Make a saturated salt solution. Fill a tall glass with warm water and stir in table salt a spoonful at a time — roughly six tablespoons per cup — until no more dissolves.
2. Float the die. Drop it in; it should float. If it sinks, add and dissolve more salt until it does.
3. Spin and observe. Gently flick the die to spin it in the water and note which face ends up on top. Repeat 10-20 times.
4. Read the result. If the same one or two numbers keep floating up, the die is weighted toward the opposite side and is likely unbalanced. If the top face varies with no strong pattern, the die is well balanced.

Note: rinse and dry your dice afterward, especially metal or coated dice. The float test only works on plastic dice — metal dice are far denser than salt water and will simply sink.

A more rigorous check: the roll test

If you want data rather than a quick check, roll a single die a large number of times — 100 as a minimum, more is better — and tally how often each number appears. Over many rolls, each face should appear roughly the same number of times. A face that shows up far more or far less than expected suggests bias. Statisticians formalize this with a chi-square test, but for tabletop purposes, a clear, repeated skew across a few hundred rolls is enough to be suspicious.

Why are some dice unbalanced?

Almost every fairness problem traces back to manufacturing:

• Air bubbles or voids from casting create a light spot that biases the die — the most common culprit in cheaply made resin dice.
• Off-center cavities or uneven density shift the center of mass away from the middle.
• Deep, unevenly filled numbers can remove slightly different amounts of material from each face.
• Warped or inaccurate faces from poor moulds or finishing change how the die settles.

This is exactly why production quality matters. Processes like vacuum degassing (to remove bubbles from resin), consistent casting, and stage-by-stage inspection exist to keep dice balanced. Our manufacturing process guide walks through the QC checkpoints, and the sharp-edge vs rounded guide explains why edge style, contrary to a common myth, is not what determines fairness.

Frequently asked questions

How do I know if my dice are fair?

Float a plastic die in saturated salt water, spin it repeatedly, and see if the same faces keep coming up (a sign of bias). For any die, roll it 100+ times and check that each number appears roughly evenly.

What is the salt water dice test?

A buoyancy test: dissolve enough salt to float the die, then spin it. A balanced die shows random faces on top; an unbalanced one keeps floating its lighter faces up.

What makes dice unbalanced?

Uneven internal density — usually an air bubble, void, or off-center cavity from casting — plus unevenly filled numbers or inaccurate faces. They are manufacturing issues.

Does the salt water test work on metal dice?

No. Metal dice sink in salt water. They are machined to tight tolerances, so use a large roll test or rely on the maker's QC instead.