Dicelab

D&D Dice Roller & Probability Calculator

Advanced dice notation with advantage, critical hits, and D&D Beyond integration.

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Simple Dice Roller Mode

Enter your dice expression and roll instantly - perfect for quick D&D 5e rolls.

Simple mode is for one-off rolls. Use Notebook to save aliases or multi-step calculations.

Examples

Click an example to try it:

Single d20 roll

Roll a twenty-sided die.

d20
Percentile roll (d100)

Roll a hundred-sided die for percentile checks.

d100
Advantage on a d20

Roll two d20s and keep the higher result.

d20 adv
Disadvantage on a d20

Roll two d20s and keep the lower result.

d20 dis
Ability score roll

Roll 4d6 and drop the lowest die.

4d6 dl 1
Character creation

Roll 6 ability scores at once.

(4d6 dl 1) ^ 6
Reroll 1s and 2s on damage

Infinite rerolls for 1s and 2s, then add modifier.

2d6 rr 1 rr 2 + 3
Reroll 1s once on each die

Each die rerolls a 1 once if it comes up.

4d6 ro 1
Fireball damage

Roll 8d6 fire damage for the Fireball spell.

8d6
Skill check vs DC 15

Returns 1 on success, 0 on failure.

(d20 + 6) >= 15
Spell save: half damage on success

Half damage on a successful save, full on failure.

(d20 + 2) >= 15 ? 4d6 : 8d6
Basic attack vs AC 15

Attack roll with crit tracking and damage on hit.

(d20 attack + 6) >= 15 ? 2d6 + 4 : 0
Attack with advantage

Roll with advantage and apply damage on hit.

(d20 adv attack + 6) >= 15 ? 2d6 + 4 : 0
Extended crit range (19-20) and advantage

Crits on 19 or 20, with advantage.

(d20 adv attack crit19..20 + 6) >= 15 ? 2d6 + 4 : 0
Crit doubles all dice

On a crit, all dice in the damage expression are doubled.

(d20 attack + 6 oncrit double_all) >= 15 ? 2d6 + 4 : 0
Crit maximizes bonus dice

On a crit, the damage dice are maximized instead of rolled twice.

(d20 attack + 6 oncrit max_second_dice) >= 15 ? 2d6 + 4 : 0
Elven Accuracy

Triple advantage—roll 3d20 and keep the highest.

(3d20 kh 1 attack + 7) >= 17 ? 1d8 + 4 : 0
Multiattack

Repeat the attack expression 3 times and sum.

((d20 attack + 5) >= 15 ? 1d8 + 4 : 0) ^ 3
Analyze 3d6 distribution

View the probability distribution for 3d6.

analyze 3d6
Compare advantage vs normal

Compare probability curves side by side.

analyze 2d20 kh 1 + 5, d20 + 5
Paladin attack with bless

Analysis of a paladin under effects of bless with 2 attacks, with +8 to hit, against an AC of 15, holding a d10 weapon with +5 damage modifier and doing divine smite on crits.

analyze (d20 adv attack crit19..20 + 8 as a1 + d4 > 15 ? (1d10 + 5 + (a1.crit ? 2d8))) + (d20 adv attack crit19..20 + 8 as a2 + d4 > 15 ? (1d10 + 5 + (a1.crit == 0 ? (a2.crit ? 2d8))))

Dice Notation Reference

  • Roll dice with modifiers: 2d20 adv + 5, 1d100, or 3d8 + 2.
  • Use filters with spaces: 4d6 dl 1, 6d6 kh 3, 5d4 rr 1, 4d6 ro 1, or 2d20 dis.
  • Abbreviations: adv/dis (advantage/disadvantage), kh/kl (keep high/low), dh/dl (drop high/low), rr (reroll matching results), and ro (reroll matching results once).
  • Elven Accuracy (triple advantage): when you have advantage on an attack, roll three d20s and keep the highest, e.g. 3d20 kh 1 attack + 7.
  • Mark attack rolls by adding attack to a d20 expression to enable crit tracking. Attacks crit on a natural 20 by default and apply oncrit double_dice unless you override them with ranges like crit19..20 or modes like oncrit max_second_dice and oncrit double_all; crits only apply when paired with attack, and auto-hit logic uses the kept d20 after advantage or disadvantage.
  • Branch with ternary logic: condition ? then : else treats non-zero as true and defaults the missing else side to 0.
  • Repeat expressions with the caret operator: 1d6 ^ 3 rolls 1d6 three times and adds the results; the right side must be a non-negative number.
  • Assign variables once and reuse them across cells: let base = 2d8 + 3 then reference with base + 1d4.
  • Create aliases for quick reuse: let smite = 2d8 then roll smite + 1d6 in any cell.
  • Analyze probability mass functions with analyze 3d6 or comma-separated inputs like analyze 1d4 + 2, smite to view means, ranges, and quantiles.
  • Import a D&D Beyond character by entering its numeric ID (or share link) and pressing Import.
  • Use per-cell logs to decide how much detail you want while you work.

Frequently Asked Questions

Does Dicelab work without JavaScript?
The calculator requires JavaScript and WebAssembly, but the guide and examples below are readable without it.
What dice notation does Dicelab support?
Dicelab supports standard dice notation like 2d6+3, plus advanced modifiers like advantage (adv), disadvantage (dis), keep highest (kh), drop lowest (dl), reroll (rr/ro), attack rolls with crits, and probability analysis.
Can I import my D&D Beyond character?
Yes! Enter your D&D Beyond character ID or share link to auto-generate aliases for your attacks and abilities.
What is Notebook mode?
Notebook mode lets you create reusable aliases with 'let', keep multiple cells with logs, and build complex character sheets for repeated use.
What is the difference between Simple and Notebook mode?
Simple mode is a compact interface for quick rolls, while Notebook mode provides a more detailed workspace with cell logging, aliases, and reusable cells.
Why would I want to use Dicelab?
Dicelab is a free dice roller for D&D 5e and tabletop RPGs. It supports advanced dice notation, probability analysis, and D&D Beyond integration. It is a great tool for both optimizers and more casual players.

Ctrl/Cmd + Enter evaluates the focused cell

Notebook