Is this dice roller truly random?
It uses JavaScript's Math.random(), which is a pseudo-random number generator (PRNG). Outputs are statistically uniform and indistinguishable from random for games, classroom demonstrations, and most simulations, but they are not cryptographically secure. For high-stakes randomness (gambling audits, cryptographic keys, security tokens), use a certified true random source such as random.org or a hardware RNG.
What does notation like 3d6+2 mean?
Standard dice notation is NdS+M: roll N dice each with S sides, then add modifier M. So 3d6+2 means roll three six-sided dice and add 2 to the sum. The modifier can be negative (e.g., 1d20-1). With Dice Type = d6, Number of Dice = 3, and Modifier = 2, this calculator produces the same result.
Can I roll dice with different numbers of sides at the same time?
Not in a single roll on this calculator — the form rolls N dice of one chosen type. For mixed pools like 1d8 + 2d6, run two separate rolls and add the totals manually. The math is identical: each die contributes its own independent draw, and expected values add linearly.
What is the expected value of NdS?
For a single S-sided die, the expected value is (S+1)/2 — that's 3.5 for d6, 10.5 for d20. For N dice, expected value is N times (S+1)/2, plus any modifier. So 3d6+2 has expected value 3 x 3.5 + 2 = 12.5. The Maximum Possible field shows N x S + M, the absolute ceiling.
Why do sums of many dice cluster in the middle?
Each die is independent and uniformly distributed, but their sum is not uniform — the central limit theorem says the sum of many independent draws approaches a normal (bell-shaped) distribution. With 2d6 there are six ways to roll a 7 but only one way to roll a 2 or a 12, so 7 is six times more likely. The more dice you roll, the tighter and more symmetric the bell becomes.
How is this different from random.org?
Random.org generates numbers from atmospheric noise — true randomness with no algorithmic seed. This tool uses your browser's PRNG, which is deterministic given its internal state but practically unpredictable for casual use. Both are fine for games; only true RNG is appropriate for lotteries, audits, or any context where reproducibility or seed recovery would matter.
Can I get the same roll twice on purpose (seeding)?
No — Math.random() doesn't expose a seed in standard browsers, so you can't reproduce a specific sequence. If you need reproducible rolls (for tutorials, fair play verification, or debugging), use a seeded PRNG library such as seedrandom.js or a system that publishes verifiable random outputs.
Why is the d100 listed even though no physical die has 100 sides?
A d100 (or percentile die) is conventionally rolled as two d10s — one for tens, one for ones — giving a uniform result from 1 to 100. Physical pentagonal trapezohedra exist but are rare. This calculator simulates a d100 directly with a uniform draw from 1 to 100, which is mathematically identical to the two-d10 method.
