Generate random numbers from a seed: integers in a range, decimals, lottery-style draws without repeats and dice rolls, repeatable with xoshiro256**.
These 10 numbers come from seed “2026”: anyone using the same seed and settings gets exactly the same list, which makes draws auditable. Pseudorandom output like this is fine for games, sampling and simulations but not for passwords or cryptographic keys.
The seed 2026 is used directly as the 64-bit starting value.
SplitMix64, started from the seed, fills the four 64-bit words of xoshiro256**, which then produces one 64-bit output per step.
Rejecting the top sliver of outputs makes every value exactly equally likely. Results depend only on the seed; an unseeded mode using fresh entropy is not implemented in this calculation.
Numbers come from xoshiro256**, a 64-bit pseudorandom generator by Blackman and Vigna with a period of 2²⁵⁶ − 1, whose starting state is filled from your seed by SplitMix64. Each 64-bit output x becomes min + (x mod m), where m is the number of possible values, after outputs from the top sliver of the 64-bit range are thrown away so that every value is exactly equally likely. Decimals are drawn as whole numbers of 10⁻ᵈ steps and divided back.
The default draws 10 integers from 1 to 100 with seed 2026: 10, 13, 19, 87, 95, 37, 73, 40, 32, 34. Anyone who enters the same seed and settings gets the same list, so raffle draws, classroom samples and simulations can be checked afterwards.
A seed-driven list is predictable to anyone who knows or guesses the seed, so it is unsuitable for passwords, encryption keys or prize draws where the seed is not published in advance.
Checked against: Independent Python transcription of Vigna's splitmix64.c and xoshiro256starstar.c with the same rejection mapping (scratch script; its SplitMix64 matches the published seed-0 value 0xE220A8397B1DCDAF)
Checked against: Same Python reference implementation
Checked against: Same Python reference implementation (integer draw in [0, 1000], divided by 10³)
Checked against: Python reference; the text seed hashes to FNV-1a 64 0xa430d84680aabd0b, the published FNV-1a hash of “hello”
No, they are pseudorandom: a fixed calculation turns the seed into a sequence that looks random but repeats exactly for the same seed. That suits games, sampling and simulation. Passwords and keys need a cryptographically secure generator, such as the browser's crypto.getRandomValues or a deterministic random bit generator specified in NIST SP 800-90A, which an observer cannot predict from past outputs.
The seed sets the generator's starting state, so the same seed and settings always give the same numbers on any device. A whole-number seed from 0 to 18,446,744,073,709,551,615 (2⁶⁴ − 1) is used directly; any other text is hashed with 64-bit FNV-1a. For example, 3 six-sided dice with the seed hello always roll 1, 6, 1.
Set the range to 1–49, How many to 6 and turn on No repeats; a duplicate is redrawn until 6 different numbers remain. Each of the C(49, 6) = 13,983,816 possible sets is equally likely, including 1, 2, 3, 4, 5, 6. Turn on Sort the results to list them in order, as lottery tickets do.
Because the plain remainder favours some values whenever the range doesn't divide the number of possible outputs. A toy generator with 8 outputs (0–7) mapped to 3 values by x mod 3 gives remainders 0, 1, 2, 0, 1, 2, 0, 1, so two values get 3/8 and one gets 2/8. Rejecting outputs 6 and 7 makes each value exactly 1/3; this calculator applies the same rule to its 2⁶⁴ outputs.
Accuracy depends on your inputs and the method's assumptions. Decimal arithmetic uses 50 significant digits, but estimates, numerical methods and source data can be less precise; the displayed rounding does not remove those limits. It is checked against 6 worked examples whose answers come from independent sources; for example, “Ten integers 1–100, seed 2026 (defaults)” is checked against Independent Python transcription of Vigna's splitmix64.c and xoshiro256starstar.c with the same rejection mapping (scratch script; its SplitMix64 matches the published seed-0 value 0xE220A8397B1DCDAF).
Blackman & Vigna, Scrambled linear pseudorandom number generators (xoshiro256**), ACM TOMS 47(4), 2021; Steele, Lea & Flood, Fast splittable pseudorandom number generators (SplitMix64), OOPSLA 2014; Fowler–Noll–Vo hash, FNV-1a 64-bit parameters (IETF draft-eastlake-fnv).
6 worked examples with independently sourced answers ship with this calculator. They run in the test suite; you can run them here too.
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