Dice Roller

This online dice roller simulates rolling any number of dice, each with any number of sides, and adds a flat modifier to the total. The tool mirrors the notation used in tabletop roleplaying games: NdS+M, where N is the number of dice, S is the number of sides on each die, and M is an optional positive or negative modifier.

When you click Roll Dice, the calculator generates one random integer per die, uniformly distributed between 1 and the number of sides (inclusive), then sums all results and adds the modifier. For example, rolling 2d6+3 rolls two six-sided dice, adds the two face values together, and then adds 3 to that sum.

The tool supports between 1 and 20 dice at a time and between 2 and 100 sides per die, covering everything from the classic d6 through the percentile d100 used in many RPG systems. Modifiers can be any positive or negative integer, representing ability score bonuses, proficiency bonuses, situational penalties, or any other flat adjustment a game rule applies.

A roll history stores up to the last 20 rolls in your session, showing each roll's full notation, individual die results, and final total. After multiple rolls, session statistics appear automatically, displaying the total number of rolls made, the running average, and the highest and lowest totals you have recorded. This makes it easy to spot streaks, verify probability over time, or track a character's damage output across a combat encounter.

The dice notation system (also called RPG dice notation or dice algebra) is a compact shorthand universally adopted across tabletop roleplaying games, wargames, and board games. Once you understand it, you can read any rulebook or module without confusion.

The basic format is NdS: the letter d stands for "die" or "dice," the number before it is how many dice to roll, and the number after it is the number of sides. So 3d8 means "roll three eight-sided dice and add them together." When there is only one die, the leading 1 is often omitted: d20 is the same as 1d20.

Modifiers are appended after the die code with a plus or minus sign: 2d6+5 means roll two six-sided dice, sum them, then add 5. A negative modifier looks like 1d20-2. Modifiers commonly represent ability score bonuses (Strength, Dexterity, etc.), proficiency bonuses, magic item bonuses, or spell-imposed penalties.

Understanding this notation lets you configure the dice roller precisely for any rulebook instruction. Select the number of dice and sides to match the notation, enter your modifier, and roll.

Each die in this roller is a fair, uniform random variable: every face has an equal probability of appearing. For a single die with S sides, the probability of any specific face is exactly 1/S. For a d6, that is 1/6 ≈ 16.67%; for a d20, it is 1/20 = 5% per face.

When you roll multiple dice and sum them, the distribution of totals is no longer flat — it follows a discrete probability distribution that increasingly approximates a bell curve (normal distribution) as the number of dice grows. This is a direct consequence of the Central Limit Theorem. With 2d6, totals of 6, 7, and 8 are far more likely than 2 or 12. With 4d6, the middle values cluster even more tightly.

Key statistics for NdS+M rolls:

• Minimum possible total: N × 1 + M = N + M
• Maximum possible total: N × S + M
• Expected value (mean): N × (S + 1) / 2 + M
• Variance: N × (S² − 1) / 12

For a standard 1d6, the expected value is (6 + 1) / 2 = 3.5. For 2d6, it is 2 × 3.5 = 7. The session statistics panel in the roller tracks your running average, which should converge toward the theoretical mean as you accumulate more rolls.

A critical success (rolling the maximum on the die) and a critical failure (rolling 1) each have a probability of 1/S. On a d20 that is a 5% chance for each, which is why D&D 5e critical hits feel exciting but not overwhelming — they occur roughly once every 20 attack rolls before any advantage or disadvantage is considered.

The dice roller covers virtually every situation you will encounter in popular tabletop RPG systems. Here are the most frequent use cases and the dice configurations they require.

Dungeons & Dragons 5th Edition

D&D 5e relies almost entirely on the d20 for its core resolution mechanic: every attack roll, saving throw, and ability check is 1d20 plus relevant modifiers. Damage rolls use a variety of dice depending on the weapon or spell. Ability score generation uses 4d6 (drop the lowest, which you can approximate by rolling 4d6 and discarding the smallest value manually). Hit points at level-up use the character class's hit die (d6 through d12) plus Constitution modifier.

Pathfinder

Pathfinder 2e uses a similar d20-based system. Spells and abilities often add multiple dice — for example, fireball deals 6d6 fire damage. Increasing spell level adds more dice, making the multi-dice feature of this roller especially useful.

Warhammer Fantasy Roleplay

WFRP uses d10 and d100 (percentile) rolls for skill tests. The d100 is rolled as two d10s read as tens and units, giving a result from 01 to 100. The d100 preset in this roller simulates that directly.

Board Games and Wargames

Many board games use 2d6 or 3d6 for movement or combat resolution. Wargames such as Warhammer 40,000 use pools of d6 for hit and wound rolls. This roller handles pools of up to 20 dice at once, covering most practical wargame scenarios.

Probability Experiments and Education

Teachers and students use virtual dice to demonstrate probability, the law of large numbers, and the Central Limit Theorem without needing physical dice. Roll the same configuration many times and watch the session average converge toward the theoretical expected value — a vivid, interactive statistics lesson.

Whether you are playing face-to-face with physical dice or running an online session over a virtual tabletop (VTT), this free online dice roller fits seamlessly into your workflow. Here are practical suggestions for getting the most out of it.

Bookmark quick presets mentally: The preset buttons (d4 through d100 and multi-die combos) let you switch dice types in one click. Before a session, identify which dice you use most — your weapon damage die, your spell dice, your hit die — and get familiar with selecting them quickly so rolls do not interrupt the narrative flow.

Use the modifier field for everything flat: Instead of rolling then doing mental arithmetic, enter your full modifier (ability bonus + proficiency + magic bonuses) into the modifier field before rolling. The calculator adds it automatically and displays the corrected total, reducing calculation errors during fast-paced combat.

Track advantage and disadvantage manually: D&D 5e's advantage rule calls for rolling two d20s and taking the higher (advantage) or lower (disadvantage). Set the dice count to 2 and the sides to 20, roll, then apply the higher or lower value as your final result — the individual die values are shown for exactly this purpose.

Session history as a cheat-sheet: The roll history log lets you verify a total after a moment of distraction, or show other players that a critical hit result is genuine. Up to 20 entries are stored, which covers most combat encounters.

Clear history between encounters: Use the Clear button after each encounter to reset the session statistics. This gives you a clean average for the new fight rather than mixing old and new data.