Dice Notation Explained: A Complete Guide to NdX
If you have picked up a tabletop RPG rulebook for the first time, the notation can look like a foreign language. Phrases like "roll 2d6 for damage", "make a 1d20 ability check" or "roll 4d4+4 for hit points" appear on nearly every page. Once you understand the pattern, it clicks instantly — and you realise it is a remarkably compact way to describe any dice roll.
The basic format: NdX
Dice notation follows a simple formula: NdX, where N is the number of dice to roll and X is the number of sides on each die. The "d" stands for "die" or "dice".
So 2d6 means roll two six-sided dice and add the results. 1d20 means roll one twenty-sided die. 4d4 means roll four four-sided dice and add them together. The notation is always number-of-dice, then "d", then sides-per-die.
When a modifier is added — like 2d6+3 — it means roll the dice, sum the results and then add (or subtract) the fixed number. So 2d6+3 produces a result between 5 and 15.
Every standard polyhedral die
A standard RPG dice set contains seven types. Here is what each one is used for:
| Die | Range | Common uses |
|---|---|---|
| D4 | 1–4 | Damage for small weapons (daggers, darts). Healing for minor potions. One of the least satisfying dice to roll physically — it has no clear "top" face. |
| D6 | 1–6 | The everyday cube. Damage for shortswords and many spells. Also used in wargames, board games and traditional dice games. The most recognisable die in existence. |
| D8 | 1–8 | Damage for longswords and rapiers in D&D. Hit dice for certain character classes. Less common outside RPGs but appears in some wargames. |
| D10 | 1–10 (or 0–9) | Damage for heavy crossbows and some two-handed weapons. Also used in percentile rolls as part of a D100. Often sold in pairs marked 1–10 and 00–90. |
| D12 | 1–12 | Damage for greataxes in D&D. Hit dice for Barbarians. One of the rarer dice — outside RPGs, it sees limited use. Rolling a 12 on a D12 for greataxe damage feels appropriately dramatic. |
| D20 | 1–20 | The most iconic die in tabletop RPGs. Used for almost all ability checks, attack rolls and saving throws in D&D and Pathfinder. Rolling a natural 20 is a critical hit; rolling a 1 is a critical failure in many systems. |
| D100 (or percentile) | 1–100 | Used for wild magic surges, random encounter tables, percentage chances and system-specific mechanics. Usually rolled by combining two D10s: one showing tens (00, 10, 20…) and one showing units (0–9). A roll of 00 and 0 equals 100. |
Multi-die rolls and why they matter
Rolling multiple dice produces a different distribution than rolling one die. When you roll 1d6, every result from 1 to 6 is equally likely. When you roll 2d6, the results are not equally likely — combinations that sum to 7 are far more probable than combinations that sum to 2 or 12, because there are more ways to get 7 (1+6, 2+5, 3+4, 4+3, 5+2, 6+1) than there are to get 2 (only 1+1).
This is why designers choose different dice combinations for different effects. A 1d20 check produces a flat distribution — every result from 1 to 20 is exactly 5% likely, which means both success and failure feel genuinely uncertain. A 2d10 check produces a bell curve centred around 11, where middling results are more common and extremes are rarer. Game designers use this deliberately to shape how often characters succeed and fail.
Advantage and disadvantage in D&D 5e
Fifth Edition Dungeons and Dragons introduced a mechanism called advantage and disadvantage. When you have advantage on a D20 roll, you roll two D20s and take the higher result. When you have disadvantage, you roll two and take the lower. This is often written as 2d20kh1 (roll 2d20, keep the highest 1) or 2d20kl1 (keep the lowest 1) in digital dice tools.
Mechanically, advantage increases your effective average roll from 10.5 to about 13.8, while disadvantage drops it to about 7.2. It is a significant swing — roughly equivalent to a +3 or -3 modifier — and was designed to replace the older system of stacking numerical bonuses and penalties.
Dropped dice notation
Another common variation is drop-lowest notation. When creating a D&D character using the classic method, you roll 4d6 and drop the lowest result. This is written as 4d6kh3 (roll four D6s, keep the highest three). The range for a single ability score this way is 3–18, but the average is around 12.2 rather than 10.5 for a straight 3d6, because the lowest result is discarded.
Non-standard dice
Not all dice notation refers to physical dice. Digital tools and tabletop systems sometimes use dice with unusual numbers of sides: D2 (effectively a coin flip), D3 (often simulated by rolling a D6 and halving), D30 (rare but real), and theoretical dice like D7 or D13 that exist as digital concepts even if physical versions are uncommon. The notation works the same way regardless of the number of sides.
Roll any die online — from D4 to D100 — using the Dice Roller. Roll multiple dice at once and get individual results plus a total. No physical dice required.
Reading dice notation at a glance
Once you have the pattern, any dice notation is readable in seconds. 3d8+5: three eight-sided dice, add the results, then add 5 (range: 8–29). 1d100: one percentile roll (range: 1–100). 2d6-1: two six-sided dice summed, minus 1 (range: 1–11). The compact notation carries a lot of information in very few characters, which is exactly why tabletop RPG designers adopted it and it has stuck for decades.
This guide covers standard dice notation as used in tabletop RPGs. Specific rules may vary by game system.