Single die
Roll a d8
A 8-sided die, rolled in your browser. Every face has an equal 12.5% chance, which works out to 1 in 8.
The odds on a d8
A single die is flat: no total is more likely than any other. The curve only appears once you roll more than one, which is what the odds calculator is for.
- Lowest
- 1
- Highest
- 8
- Average
- 4.50
- Each face
- 12.5%
- Odds
- 1 in 8
Every bar the same height. That flatness is the whole point of a single die: 12.5% per face, no favourites.
What a d8 is for
Longsword and rapier damage, and hit dice for the middleweight classes.
The middleweight
An octahedron is two square pyramids glued base to base, and it is the best rolling die in the standard set: enough faces to tumble properly, few enough that it settles fast. If a die is going to end up cocked against a book, it is rarely this one.
In play the d8 sits at the exact point where a weapon is worth taking with one hand. A longsword or rapier averages 4.5, which is a point better than a shortsword and three worse than a greataxe, and that gap is the entire design of the weapon table. It is also the standard healing die, which is why a 1d8 spell scaled up appears as 2d8, 3d8 and 4d8 so often.
One thing worth knowing: a critical hit doubles the weapon dice, so a d8 weapon crit is not a d8 with a bonus, it is 2d8. That changes the shape as well as the average. A flat 1 to 8 becomes a hump centred on 9, and the chance of rolling badly collapses.
Hitting a target number
What a flat d8 beats, and how much two-dice advantage moves it.
| Need | Flat | Advantage | Disadvantage |
|---|---|---|---|
| 2+ | 87.5% | 98.4% | 76.6% |
| 3+ | 75.0% | 93.8% | 56.2% |
| 4+ | 62.5% | 85.9% | 39.1% |
| 5+ | 50.0% | 75.0% | 25.0% |
| 6+ | 37.5% | 60.9% | 14.1% |
| 7+ | 25.0% | 43.8% | 6.25% |
| 8+ | 12.5% | 23.4% | 1.56% |
How to use this roller
Tap the die or press the roll button. To roll several at once, change How many, and the chart above redraws to the distribution you are actually rolling. To add a bonus, put it in Modifier: entering 3 turns a d8 into 1d8+3. Negative numbers work for penalties. The keyboard shortcut is R. After a roll, Copy link gives you a URL that shows exactly that result to whoever opens it.
Nothing is stored on a server and no account is needed. The page works offline once loaded, which matters if the venue has poor signal.
Common questions about the d8
What are the odds of rolling a 8 on a d8?
The odds of rolling a 8 on a d8 are exactly 12.5%, or 1 in 8. Every face on a fair d8 is equally likely, so a 8 is no rarer than any other number.
Should you roll a d8 hit die or take the fixed value?
Taking the fixed value is better on average. The fixed hit points for a d8 hit die are 5, against an average roll of 4.5, so every level you roll costs half a hit point in expectation. A roll only beats the fixed 5 when it shows 6, 7 or 8, which is 37.5% of the time; it ties 12.5% of the time and falls short 50% of the time.
Why is the d8 the easiest die to read?
A d8 settles quickly with one face lying flat on the table and its opposite face pointing straight up, so the result is never ambiguous. A d4 has no top face at all, and a d20 has so many small faces that it can stop on an edge against a book or a tray wall.
What is the average roll on a d8?
The average roll on a d8 is 4.5. That is the midpoint of 1 and 8, and the average of any die is always (sides + 1) divided by 2. Over many rolls your results converge on it, but any single roll tells you nothing.