Random Number Generator – Range & Dice

The generator maps a uniform fraction r ∈ [0,1) onto your integer range using min + ⌊r × span⌋, so every value from min to max is equally likely. Rolling a die is the range 1–6 (span 6): each face has probability exactly 1/6 ≈ 16.67%, and across 600 rolls you should see roughly 100 of each — the tool can batch-generate that sample. A lottery-style 1–49 draw, a 0–100 percentage, or a custom 10–99 span all use the same mapping with the span adjusted. Entering an optional seed makes the sequence reproducible — the same seed regenerates the same numbers, which is how experiments and unit tests stay repeatable. Without a seed, system entropy drives each fresh run. The tool reports the theoretical probability 1/span per value and flags the common bias trap of using modulo on raw floats instead of the floor mapping.

1. 1

   Set the range

   Minimum and maximum, inclusive — e.g. 1 and 6 for dice

2. 2

   Choose the count

   Generate one value or batches like 600 rolls

3. 3

   Optionally seed

   Same seed → same sequence, ideal for testing

4. 4

   Read the output

   Values, plus the uniform probability 1/span per number

• 1

  Uniform output: each of the span values carries probability 1/span

• 2

  Seeds make randomness reproducible on demand

• 3

  Inclusive ranges need the +1 in the span: 1–6 spans 6 values

• Forgetting the +1 so a 1–6 request only ever returns 1–5

• Expecting short runs to look even — 10 rolls can easily show one face 4 times

• Reusing one seed when independent sequences are required

• Assuming lottery memory: past draws never change the 1-in-13,983,816 odds