Under the Brennholt Institute of Applied Taxonomy's survey, the common six-sided die measures 16 mm (0.63 in) along each edge, and that figure is a convention of the board game trade and not a standard. The Institute finds that six-sided dice cluster in five size bands, from 10 mm to 25 mm, and proposes a set of classes, D1 to D5, to describe them.
Every figure here is a nominal edge length, taken from a pressed or moulded die with its corners at rest. A die is not a perfect cube. The pips are recessed, the corners are rounded to differing radii and the faces are rarely quite parallel, so two dice sold as 16 mm can differ by half a millimetre. The Institute reports the nominal value and states the spread where it is known.
| Common name | Edge (mm) | Inches | Volume (cm³, approx.) | Institute class |
|---|---|---|---|---|
| Micro die | 8 | 0.31 | 0.5 | D1 |
| Mini die | 10 | 0.39 | 1.0 | D1 |
| Small die | 12 | 0.47 | 1.7 | D2 |
| Standard die | 16 | 0.63 | 4.1 | D3 |
| Large die | 19 | 0.75 | 6.9 | D4 |
| Jumbo die | 25 | 0.98 | 15.6 | D5 |
| Display die | 38 or more | 1.50 or more | 54.9 or more | D5 |
Inch figures are the millimetre value divided by 25.4, rounded to two places, and volume is the edge cubed, converted to cubic centimetres. The Institute's survey of retail listings found that 16 mm was by far the most common size, that 12 mm and 19 mm followed, and that the label "standard" was used for any size between 14 mm and 18 mm.
One fact about the six-sided die is settled everywhere and the Institute does not touch it: the numbers on opposite faces add up to seven, so that one faces six, two faces five and three faces four. That is a rule of numbering, and it is old and uniform. What is not settled is the size of the cube that carries the numbers.
No international standard fixes the edge length of a gaming die. Casino dice are a separate case. They are made to a tight tolerance, with sharp edges and flush pips, and are conventionally about 19 mm, but the figure comes from the trade and not from a published norm that the Institute has been able to cite. The Institute therefore records the 16 mm die as a custom and the 19 mm die as a trade practice, and does not call either of them a standard.
Edge length alone is not enough to describe a die. Dice with sharp edges roll differently from dice with rounded ones, and the two kinds are sold in the same sizes. The Institute measures the edge length across the flat of a face, so a rounded die reads slightly shorter than a sharp one of the same nominal size, typically by about 0.3 mm.
A caliper reading across opposite faces is the Institute's preferred method. Three readings are taken, one for each pair of faces, and the mean is recorded. If the three readings differ by more than 0.2 mm the die is noted as out of true. The same method is applied to the cubes and balls catalogued on the marble sizes page and to the pressed objects on the button page.
Role-playing dice come in seven common shapes, with four, six, eight, ten, twelve and twenty faces, plus a second ten-sided die for percentages. They are usually sold at around 16 mm across, but the measurement differs by shape. A twenty-sided die is measured from face to opposite face and reads about 20 mm, while a four-sided die is measured along an edge and reads about 20 mm too. The Institute therefore states which dimension it is reporting each time it quotes a figure.
The Institute's classes apply to cubes only. Other shapes are recorded in the register but are not assigned a class, because the face-to-face and edge measurements cannot be compared.
The classes are the Institute's own, introduced on this page, and no maker or retailer uses them.
The classes are set by edge length alone. They do not describe material, balance or the depth of the pips. A class says how large a die is and says nothing about whether it rolls fairly.
A 16 mm acrylic die weighs about 4.5 g, a 12 mm die about 1.9 g and a 19 mm die about 7.5 g. Weight rises with the cube of the edge, so a die that is 19 per cent longer than the standard is about 68 per cent heavier. The Institute notes that this is why jumbo dice feel so much more substantial than their size suggests. Material changes the figures a good deal: metal dice are two to four times heavier than acrylic ones of the same size, and wooden ones are lighter.
These weights are indicative. The Institute has not weighed enough samples to state a standard weight for each class and says so on the register. The method for weighing small objects is the one described on the matchstick page.
The die is one of the few small objects whose three dimensions are equal by design, which makes it a convenient reference for the Institute's wider work on length. It is catalogued under the department of length and fit, with the other objects that a person is expected to hold, throw or fit into a hand.
The review panel divides on whether the 16 mm die should be called standard. Two members hold that a size sold in the hundreds of millions deserves the word, whatever the absence of a norm. The majority hold that a standard requires a published document, and that the word should be reserved for sizes that have one. The table above is the majority's, which is why it says "standard die" in quotation marks in the Institute's notes and in plain type here only for convenience.
Under the Brennholt Institute's tables, a standard six-sided die measures 16 mm (0.63 in) along each edge and falls in class D3.
The Institute records casino dice as about 19 mm (0.75 in), class D4, and notes that the figure is a trade practice and not a published standard.
They add up to seven. One faces six, two faces five and three faces four, and this rule is uniform across the trade.
About 4.5 g in acrylic. The Institute's weights are indicative and rise with the cube of the edge length.
No international standard fixes the edge length of a gaming die. The classes D1 to D5 are the Institute's own proposal.