Here is D&D dice explained in two sentences. The twenty-sided die decides whether something works; all the other dice decide how much. If you understand that split, you understand most of what happens at a D&D table, and the rest of this article is detail you can learn as you go.
Dice are the most visible part of the hobby and the most intimidating to someone who has only ever rolled a pair of sixes in Monopoly. There are seven shapes in a standard set. They have a notation. Experienced players shout about “nat 20s” and “rolling with advantage.” None of this is hard; it is just unexplained.
What are the seven dice, and what is each one for?
A standard polyhedral set has seven dice, named for the number of faces. The notation “d” plus a number means “a die with that many sides,” and a number in front means “roll that many of them.” So 2d6 means roll two six-sided dice and add them.
| Die | Shape | Typical use |
|---|---|---|
| d4 | Four-sided pyramid | Small weapon damage (a dagger), small healing |
| d6 | The ordinary cube | Many weapons, many spells, the most common damage die |
| d8 | Eight-sided | Medium weapons, several healing and attack spells |
| d10 | Ten-sided | Heavier weapons, some spells; also used in pairs for percentages |
| d12 | Twelve-sided | Big two-handed weapons; the barbarian’s friend |
| d20 | Twenty-sided | Nearly every “does it work?” roll: attacks, skills, saving throws |
| d100 (percentile) | A second d10 marked in tens | Random tables and rare percentage rolls |
The d20 is the one you will roll most. It decides success or failure. The others mostly come out after the d20 has said “yes” to measure the effect: how much damage the sword does, how many hit points the potion restores.
If you buy one set, you have everything you need. If you buy a second, you can roll 2d6 without rolling the same die twice, which matters more than it sounds in the heat of a fight.
How does a d20 roll actually work?
Almost everything uncertain in D&D resolves the same way, and once you see the pattern you stop needing to ask.
- The GM decides an action is uncertain and names what kind of roll it is: an attack, a skill check, a saving throw.
- You roll the d20.
- You add a bonus from your character sheet. The bonus reflects how good your character is at that thing.
- The GM compares the total to a target number. Meet or beat it, you succeed.
That is the whole mechanic. The three kinds of rolls differ only in which bonus you add and what the target is.
- Attack rolls add your attack bonus and compare against the enemy’s Armor Class, a number that represents how hard they are to hit.
- Skill checks add a skill bonus (Stealth, Persuasion, Athletics) and compare against a Difficulty Class the GM sets. A routine task might be around 10; a hard one around 20. The GM usually does not tell you the number.
- Saving throws add a saving throw bonus and compare against a number set by whatever you are resisting, like a spell or a trap.
New players sometimes ask why one die for everything. The answer is that it makes the game teachable. You learn one procedure on night one and apply it to climbing walls, lying to guards, and dodging fireballs.
What is a natural 20, and why does everyone cheer?
A “natural” roll means the number showing on the die itself, before any bonus. A natural 20 on an attack roll is a critical hit: it hits regardless of the target, and you roll the damage dice twice. A natural 1 on an attack roll misses regardless of your bonus.
The cheering is partly math and partly ritual. The odds of any specific face on a d20 are one in twenty, five percent, so a natural 20 at a dramatic moment feels earned even though the die has no idea what is happening in the story. Groups develop traditions around them: a special die, a round of applause, a player who insists their d20 is cursed.
Note that in the standard rules the automatic critical applies to attack rolls specifically. Whether a natural 20 on a skill check is an automatic success is a common house rule, and tables vary. Ask your GM. It is a good first rules question because every GM has an opinion.
If this is useful, the newsletter sends more like it.
What do advantage and disadvantage mean?
This is the mechanic new players hear most and understand least, and it is simple.
Advantage: roll two d20s and use the higher one. Disadvantage: roll two d20s and use the lower one.
That is it. The GM grants advantage when circumstances favor you: you are attacking an enemy who cannot see you, or a friend is helping you. Disadvantage applies when things are against you: you are shooting at long range, or trying to pick a lock in the dark.
The design reason it works so well is that it replaces a pile of small plus-and-minus modifiers with one physical action. Instead of “add two for high ground, subtract one for rain,” you grab a second die. It is faster, it is memorable, and it feels good in the hand.
The math is worth knowing because it changes how you play. Rolling two dice and keeping the higher one raises your average result from 10.5 to roughly 13.8 on a d20, and nearly doubles your chance of rolling a natural 20, from 5 percent to about 9.75 percent. Advantage is worth more when you need a middling number, and less when you need a near-impossible one. In practice: if someone can help you, let them.
Why do the other dice feel so different?
Because a single die and a sum of dice have different shapes.
One d20 is flat. Every face from 1 to 20 is equally likely, so wild swings are normal. That is why a d20 decides success: the game wants drama in the “does it work?” moment.
Two d6 added together are not flat. A total of 7 is the most likely result; 2 and 12 are rare. Sums of dice cluster toward the middle, which is why damage rolls feel more predictable than attack rolls. A greatsword’s 2d6 will usually land around 7; it is the d20 before it that keeps you guessing.
This difference is the reason some other RPGs use 2d6 or dice pools for their core resolution instead of a d20. They want fewer wild swings. We touch on several of them in RPGs that aren’t D&D. Neither approach is better; they produce different moods. If you have ever argued about luck versus skill in board games, you already understand the trade.
Do you need physical dice?
No, and yes. Dice apps and online tables roll perfectly well, and plenty of groups use them without complaint.
But physical dice do something an app does not. The roll is public. Everyone watches the die tumble, and everyone sees the result at the same moment. The shared breath before it stops is a small piece of what makes a table feel like a table. A d20 that has decided three characters’ fates over two years of play becomes an object the group cares about. That is not a rules matter. It is a people matter.
A beginner’s set costs little. Buy one in a color you like. Roll it a few times at home so the shapes feel familiar. Then bring it to a table and let it embarrass you in front of friends, which is the dice’s real purpose. The game is the reason. The people are the point.
FAQ
What dice do you need to play D&D?
A standard seven-die polyhedral set: d4, d6, d8, d10, d12, d20, and a percentile d10. One set is enough to start; a second d6 and d20 are handy.
What does d20 mean?
A d20 is a twenty-sided die. In D&D it resolves nearly every question of success or failure: attacks, skill checks, and saving throws.
What is advantage in D&D?
Advantage means rolling two d20s and using the higher result. Disadvantage means rolling two and using the lower. The GM grants either based on circumstances.
Does a natural 20 always succeed?
On an attack roll, yes; it is a critical hit. On skill checks and saving throws the standard rules do not make it automatic, though many tables house-rule otherwise.
Roll with us
Subscribe to The Ludarium newsletter for new short, plain explainers like this. Want to try a game before you buy it? Play a free intro adventure in the RPG Demo Library, right in your browser, by each game’s real rules.
Get the next one in your inbox.
Board game picks, strategy, and shelf advice from The Ludarium.