D8 Dice Roller

Two pyramids glued together

An eight-sided die is an octahedron, one of the five Platonic solids: eight identical triangles, six corners, twelve edges. Hold one up and it looks like two square pyramids stuck base to base. Because every face is the same shape and the same distance from the centre, a well-made d8 is as fair as a cube.

In practice, d8s are the workhorse middle die of role-playing games. They don’t have the drama of a d20 or the swing of a d12, but they show up on a huge share of rolls once you count weapons, healing and hit points.

Where d8s get rolled

Here’s where the d8 appears in fifth edition Dungeons & Dragons. It’s not a complete list, but it covers what most players reach for in a typical session.

Rule	Roll
Longsword (one hand), rapier, morningstar, battleaxe, warhammer	1d8 damage
Longbow, light crossbow	1d8 damage
Hit Die for bard, cleric, druid, monk, rogue, warlock	1d8 per level
Cure Wounds	1d8 + modifier (2014), 2d8 + modifier (2024)
Divine Smite	2d8 radiant at its lowest level, plus 1d8 per level above
Spiritual Weapon (2014 rules)	1d8 + modifier force damage

That Divine Smite line is the big one. A paladin who lands a critical hit doubles all damage dice, including the smite, and that’s where you see someone roll a handful of d8s and the table goes quiet. Set Dice to the number you need here and the roller adds them up.

Hit points on level up

When you level up a d8 class, you can take the fixed value of 5 or roll 1d8. Rolling only beats the fixed number on a 6, 7 or 8: three faces out of eight, 37.5%. It ties on a 5 and loses on anything from 1 to 4, which is half of all rolls. The rolled average is 4.5, half a point below the fixed value. So unless your table loves the gamble, taking 5 is the better deal over a long campaign.

The single-die breakdown

Probabilities for one d8

Roll	Chance of exactly this	Chance of this or higher
1	12.5%	100%
2	12.5%	87.5%
3	12.5%	75%
4	12.5%	62.5%
5	12.5%	50%
6	12.5%	37.5%
7	12.5%	25%
8	12.5%	12.5%

The average on a single d8 is 4.5. Each face is 12.5%, one in eight.

Two d8s: the bell begins

Roll two d8s and the totals run from 2 to 16, with 9 the most common result. It’s the same shape you get with any pair of dice, just stretched.

Totals for 2d8

Total	Ways	Chance	This or higher
2	1	1.56%	100.00%
3	2	3.13%	98.44%
4	3	4.69%	95.31%
5	4	6.25%	90.63%
6	5	7.81%	84.38%
7	6	9.38%	76.56%
8	7	10.94%	67.19%
9	8	12.50%	56.25%
10	7	10.94%	43.75%
11	6	9.38%	32.81%
12	5	7.81%	23.44%
13	4	6.25%	15.63%
14	3	4.69%	9.38%
15	2	3.13%	4.69%
16	1	1.56%	1.56%

This matters for the 2024 version of Cure Wounds and for smites. With 2d8, you’ll get between 7 and 11 more than half the time. A single d8 healing spell is a gamble; two dice are noticeably more reliable.

Using a d8 outside role-playing

Eight is also a lovely number for real-world choices.

• Compass directions. Number them N, NE, E, SE, S, SW, W, NW and roll before a walk with no plan. At each junction, roll again. It’s a surprisingly good way to explore a neighbourhood you don’t know.
• Seating at a table of eight. One roll per guest, re-roll repeats.
• Eight-team brackets. The 1 to 8 number page has a full method for random brackets and lane draws.
• Octave practice. A major scale with its top note repeated spans eight notes. Music teachers roll a d8 to pick the next note to sing.

Physical d8s and why they roll so well

Pick up a cheap d8 and a cheap d20 and roll them each a few times. The d8 tumbles and stops quickly; the d20 rolls on and on, sometimes off the table. Dice with more faces are closer to a sphere, so they roll further. The octahedron is a good middle ground: it moves enough to feel random but rarely escapes the tray.

The weak point of physical d8s is the same as any plastic die: uneven moulding. Many budget dice have slightly rounded edges and small air bubbles, and some come out a hair lopsided. For casual games none of this matters much. If anyone at your table worries about a “cursed” d8, the digital version settles it, because every face here has exactly one chance in eight.

Two ways to roll a d8 without one

Before cheap polyhedral sets were everywhere, players improvised. Two tricks still work:

1. Roll a d4 and a coin. Heads adds 4, tails adds nothing. That gives 1 to 8 with equal odds.
2. Roll three coins. Treat them as binary digits (heads = 1) and add 1. Three coins give eight equally likely patterns.

Both are fair, both are slow, and both make a good probability puzzle for students. In a real game, just roll the digital die.

Advantage on a d8

Some homebrew rules and a few published features let you roll damage twice and keep the higher. On a d8, advantage moves the average from 4.5 to about 5.8 and makes an 8 come up 23% of the time instead of 12.5%. Disadvantage does the reverse: the average drops to about 3.2. Choose the mode in the roller and it’ll handle both dice for you.

For other dice, the d10 roller is next in the set, and the main dice roller has every die in one menu.

A simple d8 game for two

Here’s a quick game we use to explain the maths of two-dice totals. Each player picks a target number from 2 to 16 and then you roll 2d8 ten times. Whoever’s number came up most often wins. Players who pick 9 win far more than players who pick 2 or 16, and it only takes a couple of rounds before everyone realises the middle is where the action is.

And one last practical tip. If your character’s attack does 1d8 plus a modifier, type the modifier into the roller once at the start of a session. It stays there between rolls, so every attack only needs one click.