D12 Dice Roller
A dodecahedron: twelve pentagonal faces, and the chunkiest die in a standard set. It sits heavy in the hand and rolls with a slow, satisfying wobble. For most of D&D history it was also the least used die in the bag, which is why it usually looks brand new while the d20 next to it is scuffed.
Press Roll to throw the dice.
Press Space to roll again. Type notation like 2d6+3 or 4d6dl1 straight into the box.
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A d12 has 12 faces numbered 1–12. On a fair die every face is equally likely, so any single result comes up 8.33% of the time. Rolls run from 1 to 12, the average is 6.5, and the standard deviation is 3.45. The shape it is built from is the dodecahedron.
- Minimum
- 1
- Maximum
- 12
- Mean
- 6.5
- Median
- 6.5
- Std deviation
- 3.45
- Chance per face
- 8.33%
d12 probability
One die is flat. There is no curve and no middle to aim for, because each face has exactly one way to come up out of 12 possible results, so nothing is more likely than anything else. Add a second die and that changes immediately: totals start piling up in the middle. The dice probability guide works through why.
| Total | Ways | Probability | This or lower |
|---|---|---|---|
| 1 | 1 | 8.33% | 8.33% |
| 2 | 1 | 8.33% | 16.67% |
| 3 | 1 | 8.33% | 25% |
| 4 | 1 | 8.33% | 33.33% |
| 5 | 1 | 8.33% | 41.67% |
| 6 | 1 | 8.33% | 50% |
| 7 | 1 | 8.33% | 58.33% |
| 8 | 1 | 8.33% | 66.67% |
| 9 | 1 | 8.33% | 75% |
| 10 | 1 | 8.33% | 83.33% |
| 11 | 1 | 8.33% | 91.67% |
| 12 | 1 | 8.33% | 100% |
When you'd roll a d12
Roll a d12 when you want a wide, flat spread from one die rather than a curve from several. It suits big swingy weapon damage and it is perfect for anything already divided into twelve: months, hours on a clock face, signs of the zodiac. Designers have gradually given it more work in recent editions, so the poor thing finally gets used more than once a campaign.
Common uses
- greataxe damage in D&D 5e
- barbarian hit dice
- month or clock-face random tables
- Rolling a month, a clock hour, or a zodiac sign from a twelve-entry table
- Sorcerer and warlock damage effects that scale in large single dice
- Deciding turn order in a group of up to twelve players
d12 questions
What shape is a d12?
A regular dodecahedron, one of the five Platonic solids. Twelve regular pentagons meet three at a time at each of its twenty corners. Because the faces are wide and blunt it settles quickly, which makes it one of the calmer dice to roll on a hard table.
Why is the d12 used so little?
Historically very few things called for it. The greataxe and the barbarian hit die were about the extent of it in older editions, so a d12 could sit untouched for a whole campaign. More recent designs have added d12 effects specifically to give it something to do.
Is a d12 better than 2d6?
They are different tools. A d12 gives every result from 1 to 12 an equal shot, so extremes are as likely as the middle. Two d6s cluster hard around seven. Use the d12 when you want genuine unpredictability and the pair when you want reliability.
What can I use a d12 for outside role-playing games?
Anything that comes in twelves. Picking a month for a planning exercise, choosing an hour, drawing a zodiac sign for a writing prompt, splitting a group into a dozen slots. It is also a decent replacement for two coins and a d3 in a pinch.