Roll any dice using standard notation — 2d6+3, 4d8, d20, or several dice types at once. You get each die's face value, the modifier and the total, plus the possible range for the roll. Every face is equally likely, drawn from your browser's cryptographic random source.
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What this dice roller does
It rolls any dice you can describe in standard notation. Type 2d6+3 and it rolls two six-sided dice and adds three; type d20 for a single twenty-sided die; combine groups like 3d8+2d4-1 in one expression. You see every individual die, the modifier and the total, along with the possible range for that roll.
It is built for tabletop games, board games, probability teaching and anywhere a physical dice set is not to hand — with the advantage that these dice are perfectly balanced, which physical dice rarely are.
Dice notation explained
The notation is the standard used across tabletop gaming, and it is simpler than it looks. NdS means “roll N dice, each with S sides”. Anything after that is a modifier added to or subtracted from the total.
| Notation | Meaning | Possible range |
|---|---|---|
d20 | One twenty-sided die | 1 to 20 |
2d6 | Two six-sided dice, summed | 2 to 12 |
2d6+3 | Two d6 plus a modifier of 3 | 5 to 15 |
4d8-1 | Four d8 minus 1 | 3 to 31 |
3d8+2d4 | Three d8 and two d4, all summed | 5 to 32 |
How the rolls are generated
Every draw on this page starts with crypto.getRandomValues, the cryptographically strong random source built into your browser. That is a CSPRNG seeded from operating-system entropy: unpredictable in practice, and the right choice when a result decides something that matters. It is deliberately not described as “true randomness”, which would require a physical entropy source such as atmospheric noise or radioactive decay. Tools that claim true randomness from a browser are overstating what the platform provides.
Turning random bytes into a number in your range is where most implementations quietly go wrong. The obvious approach — take a random 32-bit value and apply % range — is biased whenever the range does not divide evenly into 2³². Some outcomes get one extra chance out of every four billion draws, which sounds negligible but is a genuine, measurable defect. This tool uses rejection sampling instead: draws landing in the incomplete final block are discarded and redrawn, so every value is exactly equally likely.
Each die in an expression is rolled independently. Rolling 4d6 is genuinely four separate draws, not one draw multiplied — which matters, because those two things have completely different distributions.
Why 7 comes up so often on 2d6
Individual dice are uniform, but the sum of several dice is not. There is only one way to roll a total of 2 (both dice show 1) and only one way to roll 12, but there are six different ways to make 7. Over many rolls, 7 appears six times as often as either extreme.
| Total on 2d6 | Ways to make it | Probability |
|---|---|---|
| 2 or 12 | 1 | 2.8% |
| 3 or 11 | 2 | 5.6% |
| 4 or 10 | 3 | 8.3% |
| 5 or 9 | 4 | 11.1% |
| 6 or 8 | 5 | 13.9% |
| 7 | 6 | 16.7% |
This is why board games that use 2d6 feel so different from games using a single d12, even though both span a similar range. The dice are fair; the distribution of their sum is not flat. Adding more dice sharpens the effect — 3d6 clusters even harder around 10 and 11.
Worked example
A typical tabletop roll:
Notation 2d6+3 Dice [5] [2] Modifier +3 Total 10 Range 5 to 15 (minimum 1+1+3, maximum 6+6+3)
Error handling
Mistyped notation gets a specific message rather than a guess. Empty input, stray letters, zero-sided dice, and unfinished expressions such as 2d6+ each produce an explanation of what could not be read and what the correct form looks like. A roller that silently interprets “2×6” as something is worse than one that asks you to fix it.
Practical uses
- Tabletop roleplaying when dice are lost, or for play-by-post games where rolls need to be pasted into a thread.
- Board games with missing dice, or with dice types the box never included.
- Teaching probability — the difference between one die and the sum of several is one of the clearest demonstrations in statistics.
- Game design — testing how a proposed dice mechanic actually distributes before committing to it.
Limitations
Up to 200 dice per group and up to 1,000 sides per die, combined across multiple groups in one expression. Advantage and disadvantage are handled by the dedicated D20 roller rather than in notation. The roller does not implement exploding dice, rerolls or keep-highest rules — those vary too much between systems to guess at.
Privacy
Rolls are generated in your browser and never transmitted. Seeded mode makes a specific roll reproducible, which is useful for play-by-post games where other players may want to verify a result.
Related tools
Flip a Coin covers the two-outcome case with tallies and best-of series. The Random Number Generator handles arbitrary ranges with uniqueness and statistics. For choosing between named options rather than numbers, use the Random Item Picker or the Wheel Spinner.
How to use the Dice Roller
- Type your dice in standard notation — for example 2d6+3, 4d8, d20, or 3d8+2d4.
- Press Roll dice to see every die's face value, the modifier and the total.
- Check the possible range shown beside the total to sanity-check the roll.
- Set Presentation to "No animation" if you prefer a still result.
- Copy the result, or export the individual dice as CSV.
Frequently asked questions
What dice notation does this roller support?
The standard form used by tabletop games: NdS for N dice of S sides, with optional modifiers. So 2d6+3 rolls two six-sided dice and adds three, d20 rolls a single twenty-sided die, and you can combine groups such as 3d8+2d4-1 in a single expression.
Are the dice fair?
Yes. Each die is an independent draw where every face has an equal chance, taken from your browser's cryptographic random source using unbiased rejection sampling. Physical dice, by contrast, are often very slightly biased by manufacturing tolerances.
Why is a total of 7 so common when rolling 2d6?
Because totals from multiple dice are not uniform even though each die is. There are six ways to make 7 with two dice but only one way to make 2 or 12, so 7 comes up six times as often. The individual dice are fair; the sum simply has more routes to the middle.
What is the biggest roll I can make?
Up to 200 dice per group, and dice of up to 1,000 sides, in expressions combining several groups. That comfortably covers tabletop use and bulk statistical rolls alike.
What happens if I type the notation wrong?
The tool tells you exactly what it could not read rather than guessing. Empty input, unknown letters, zero-sided dice and unfinished expressions such as "2d6+" all produce a specific message explaining the correct form.
Can I roll with advantage or disadvantage?
The dedicated D20 roller adds advantage and disadvantage, rolling twice per die and keeping the higher or lower value. This general roller focuses on notation, where you can express most other tabletop needs directly.
Can I reproduce a specific roll?
Yes. Switch to Seeded mode and enter a seed; the same seed and notation always produce the same roll. That is useful for play-by-post games, worked examples and testing.
