Guide • 6 min read •
D&D and Tabletop RPG Dice Guide - Standard Polyhedral Sets Explained
Modern fantasy roleplaying games rely on a standard 7-piece polyhedral dice set. This guide explains what each die does, when to roll it, and how modifiers determine action resolution.
The Standard 7-Piece Polyhedral Set
A complete tabletop roleplaying set contains seven dice:
1. **D4 (Tetrahedron)**: Dagger strikes, small healing increments, magic missiles.
2. **D6 (Cube)**: Short swords, bows, sneak attack bonuses, fireballs.
3. **D8 (Octahedron)**: Longswords, rapiers, cure wounds spells, hit dice for medium classes.
4. **D10 (Pentagonal Trapezohedron)**: Halberds, heavy polearms, eldritch blasts.
5. **D12 (Dodecahedron)**: Greataxes and barbarian fortitude.
6. **D20 (Icosahedron)**: Core action resolution, attacks, saving throws, skill checks.
7. **D100 / Percentile (Tens D10 + Units D10)**: Wild magic charts, divine intervention, loot tables.
The D20 Action Resolution Mechanic
Whenever a player character attempts an uncertain action:
1. Roll 1d20.
2. Add relevant ability modifiers (e.g. +3 Strength) and proficiency bonuses (+2).
3. Add any conditional bonuses or penalties.
4. Compare total against Target Armor Class (AC) or Difficulty Class (DC). If Total >= Target, you succeed!
Understanding Advantage and Disadvantage
When conditions strongly favor your character (like attacking a blinded foe), you roll with **Advantage**: roll 2d20 and take the higher outcome.
When circumstances hinder you (like firing through dense fog), you roll with **Disadvantage**: roll 2d20 and take the lower outcome.
Advantage shifts your expected average from 10.5 up to 13.82, while Disadvantage drops it to 7.18.
Ready to test these rolls?
Use our online dice calculator with exact probabilities and roll history.
Guide FAQ
Which die is most important in D&D?
The D20 is the most important die because it determines whether attacks, saving throws, and skill checks succeed or fail.
What is a critical hit in tabletop games?
In most 5e systems, rolling an unmodified 20 ("Natural 20") on an attack roll is an automatic hit that lets you double your damage dice.