Roll a d12: twelve-sided dice roller

How to roll the d12 on this page

The dice above are already twelve-sided. Set how many you want in Dice (1 to 6) and, if needed, move the modifier with + or −; it is applied once to the total. Then press Roll, or drag the dice with your mouse or finger and drop them in the tray.

When they stop you see each die on its own and the sum. That suits a greataxe hit in D&D (1d12 + Strength) and also games that compare two dice instead of adding them, such as Daggerheart, where what matters is which of the two d12s came out higher.

The dodecahedron: twelve pentagons

A d12 is a regular dodecahedron: 12 faces that are regular pentagons, 30 edges and 20 corners, with three faces meeting at each corner. It is the only Platonic solid with pentagonal faces. Neighbouring faces meet at about 116.6°, a wider angle than on the octahedron, so it rolls easily.

Like every Platonic solid, it is geometrically fair: any face can be moved into the position of any other by a symmetry, so none is favoured. On standard dice opposite faces add up to 13 (1 and 12, 2 and 11, 3 and 10, 4 and 9, 5 and 8, 6 and 7), one more than the number of faces, just as on the d6, d8 and d20.

Euclid constructs the dodecahedron in Proposition 17 of Book XIII of the Elements, the last of the five constructions. Plato, who had shared the other four solids among the elements, set the dodecahedron apart and wrote in the Timaeus that the god used it to arrange the constellations across the whole heaven.

The d12 in D&D: the die that rarely gets rolled

Among D&D players it is a running joke that the d12 is the most neglected die in the set, and there is something to it: even in the first edition, the d4, d8 and d12 appeared far less than the d20. In 5th edition its uses can be counted on your fingers:

A common comparison is the greataxe (1d12) against the greatsword (2d6). Both top out at 12, but the greatsword averages 7 and the greataxe 6.5. In return, the greataxe rolls 10 or more 25% of the time and the greatsword only 16.67%.

Daggerheart and other games with a d12

Daggerheart, the role-playing game from Darrington Press (Critical Role’s publisher) released in 2025, is built around the d12. Every action is resolved with the Duality Dice: two d12s of different colours, one for Hope and one for Fear. You add them, apply your modifier and compare the total with a difficulty. On top of that, it matters which die is higher: if Hope wins, the player gains a Hope; if Fear wins, the GM gains a Fear and the scene gets complicated, even if the action succeeds. If both dice show the same number, it is a critical success.

To play it here, choose 2 dice: the page shows each d12 separately, so decide beforehand which one is Hope (the left-hand one, say).

In Savage Worlds the d12 is the top step of the skill scale (d4 to d12). Against the usual target number of 4 it succeeds 9 times in 12 (75%).

Outside role-playing, 12 is a handy number: months of the year, hours on a clock face or signs of the zodiac all fit on a d12. And because 12 divides by 2, 3, 4 and 6, a single d12 stands in exactly for a d2, d3, d4 or d6.

d12 probabilities, calculated

Each face has a 1 in 12 chance, 8.33%. The average is 6.5.

Two d12s give 144 combinations. The most likely total is 13, and the distribution forms a triangle:

With Daggerheart’s Duality Dice, of the 144 combinations 66 give a higher Hope die (45.83%), another 66 a higher Fear die (45.83%) and 12 are doubles, a critical (8.33%).

Roman dodecahedra: what is known and what is not

Any search about twelve-sided dice ends up at the Roman dodecahedra, copper-alloy objects that remain unexplained. They are hollow, roughly 4 to 11 cm across, with a round hole of varying size in each of their twelve pentagonal faces and a small knob at each corner. They were cast by the lost-wax method and most date from the 2nd to the 4th century AD.

More than a hundred are known, found mainly in the empire’s north-western provinces (Gaul, Germania, Britain) and none in Italy. The first on record was shown to the Society of Antiquaries of London in 1739. In 2023 amateur archaeologists from Norton Disney in Lincolnshire found a very well-preserved one, about 8 cm tall and weighing 245 g, in an excavation with a datable context.

What matters is what is missing: no Roman text mentions them, they do not appear in mosaics or paintings, they carry no numbers or letters and they show hardly any wear. More than fifty uses have been suggested (surveying instrument, glove-knitting frame, ritual object, fortune-telling, coin gauge, die or game piece), but none has been proved. That they were gaming dice is just one of those ideas; with no numbers on the faces, there is no way to know.

Tips for using the d12