// Generator
Random Number Generator online
Generate random integers, decimals, or unique lists with custom ranges
by
CHUNKY
MUNSTER
MUNSTER
Pick the output type (integer or decimal), the range, the count, and whether duplicates are allowed. Integers are sampled inclusively on both endpoints; decimals are sampled half-open on the upper bound (min ≤ x < max), matching the underlying Math.random() convention and keeping the distribution clean at the boundary.
Unique-output mode samples without replacement and is most useful for integer draws — for example, picking 6 distinct lottery numbers from 1–49. For continuous decimals, duplicates are already vanishingly improbable, so the unique flag rarely matters there. The underlying RNG is the browser's Math.random(): well-distributed and fast, but never use it for cryptographic purposes.
Decimals are sampled half-open on the upper bound: min ≤ x < max. That matches standard library behaviour (Math.random() returns [0, 1)) and avoids floating-point edge cases at the maximum.
Up to 15 — the practical limit of IEEE-754 double precision. Beyond that the output starts running into rounding artefacts inherent to binary floating point.
It removes the chance of a literal duplicate but is rarely useful: with continuous values, repeated draws are mathematically near-impossible anyway. Unique mode is mainly intended for the integer case (drawing N distinct integers from a smaller-than-comfortable range).
Up to Number.MAX_SAFE_INTEGER (2^53 − 1) for integers. Above that the result is mathematically random but loses one-to-one mapping to integers because of float precision.
Explore the full suite of Generator tools and 290+ other free utilities at Chunky Munster.