Every D&D Die Explained and When To Use Them

Dungeons and Dragons, or D&D for short, is a beloved fantasy role-playing game that has been around for decades. One of the most important parts of the game is the use of dice, which are used to determine the outcome of various actions and events. In this post, we'll take a closer look at the different types of dice used in D&D and when to use them.

d4 - The Tetrahedron

The d4, also known as the tetrahedron, is a four-sided die with numbers from 1 to 4, one on each side. It's the smallest die used in D&D and it's often used for things like determining the damage dealt by a weapon with a low damage roll or determining the number of hit points regained by a spell.

The probability of rolling a specific number on a d4 is 1/4 or 25%, and, somewhat counter-intuitively, the average roll is not 2 but 2.5. This is because of the lack of a 0 on the die. To prove this we can add 1 + 2 + 3 + 4 = 10, that divided by the 4 sides of the die gives us the 2.5 average roll.

Examples of when to use a d4:

• When a character with a dagger attacks, they roll a d4 to determine the damage dealt.
• When a character casts magic missile, they roll one or more (depending on the level) d4s to determine the damage to the enemy.

d6 - The Cube

The d6, also known as the cube, is a six-sided die with numbers from 1 to 6, one on each side. It's the most commonly used die in D&D and it's used for a variety of actions such as determining the damage dealt by a weapon or the number of hit points regained by a spell.

The probability of rolling a specific number on a d6 is 1/6 or approximately 17%, and the average roll is 3.5.

Examples of when to use a d6:

• When a character with a sword attacks, they roll a d6 to determine the damage dealt.
• When a character casts Fireball, they roll one or more (depending on the level) d6s to determine the damage.

d8 - The Octahedron

The d8, also known as the octahedron, is an eight-sided die with numbers from 1 to 8, one on each side. It's used for actions that have a moderate range of outcomes, such as determining the damage dealt by a weapon with a moderate damage roll.

The probability of rolling a specific number on a d8 is 1/8 or approximately 13%, and the average roll is 4.5.

Examples of when to use a d8:

• When a character with a mace attacks, they roll a d8 to determine the damage dealt.
• When a character uses a spell that deals cold damage, they roll a d8 to determine the amount of damage dealt.

d10 - The Decahedron

The d10, also known as the decahedron, is a ten-sided die with numbers from 1 to 10, one on each side. one on each side. It's used in situations where a larger range of outcomes is needed, such as determining the number of experience points earned by a character.

The probability of rolling a specific number on a d10 is 1/10 or 10%, and the average roll is 5.

Examples of when to use a d10:

• When a character earns experience points, they roll a d10 to determine the amount earned.
• When a Paladin uses Blinding Smite, they roll 3 x d8 (usually notated 3d8) to determine the damage of the ability.

d12 - The Dodecahedron

The d12, also known as the dodecahedron, is a twelve-sided die with numbers from 1 to 12, one on each side. It's used for actions that have a wide range of outcomes, such as determining the damage dealt by a weapon with a high damage roll.

The probability of rolling a specific number on a d12 is 1/12 or approximately 8%, and the average roll is 6.5

Examples of when to use a d12:

• When a character with a great axe attacks, they roll a d12 to determine the damage dealt.
• When a character uses the spell Poison Spray, they will roll a d12 to determine the damage.

d20 - The Icosahedron

The d20, also known as the icosahedron, is a twenty-sided die with numbers from 1 to 20, one on each side. It's used for the most important actions in the game such as determining if an attack hits or if a character succeeds in a skill check. It's also used for determining critical hits (if you roll a 20 on the die) and critical failures (if you roll a 1).

The probability of rolling a specific number on a d20 is 1/20 or 5%, and the average roll is 10.5.

d100 - The Percentile

The d100, also known as the percentile die, although a normal d100 does not have 100 sides but only 10. A d100 is only rolled in conjunction with the d10 to get a combined results from 1-100.

The probability of rolling a specific number on a d100 d10 combo is 1/100 or 1%, and the average roll is 50.

Another uniqueness to the d100 is that it's exclusively used by the DM (Dungeon Master) and never by players. The d100 is used to attain a % probability of an outcome. 

Examples of when to use a d100:

• A DM might roll a d100 and reference it against a Treasure Table to determine the treasure available at the end of a dungeon or from a formidable enemy
• A DM might roll a d100 and, again, check it again a table to determine the results for such things as: magic item effects, artefact properties, or even effects of madness

In D&D, players will use a combination of these dice to determine the outcome of various actions. For example, a character might roll a d20 to see if they hit an enemy with their sword, and then roll a d6 to determine the amount of damage dealt.

In addition to physical dice, there are also a number of digital alternatives available, such as dice rolling apps or using virtual assistants like Google or Siri to roll a die for you. These can be a great option for those who don't have physical dice or who prefer a more convenient way to roll them. However, many players prefer the tactile experience of rolling real dice and the added element of chance that comes with it.

In conclusion, each die in D&D serves a specific purpose and has its own unique probability and average roll. Understanding when to use each die can make a big difference in the outcome of your game. Whether you prefer to roll physical dice or use a digital alternative, may your rolls be in your favor. Happy adventuring!