Random Number Generator · Practical guide
Random Number Generator With No Duplicates
Turn off Allow Duplicates and every number in the run is guaranteed unique — like drawing names from a hat.
At a glance
Quick answer
To generate random numbers with no repeats, uncheck Allow Duplicates above. Every number in the run is then guaranteed unique — the equivalent of drawing tickets from a hat without putting any back. The only rule: the range must contain at least as many integers as the count you request, so 10 unique numbers need a range of at least 10, like 1 to 10 or 1 to 100.
Interactive tool
Random Number Generator
Enter your own values, then compare the result with the examples below.
Generated Numbers
History (last 5)
With vs. Without Duplicates
| Setting | Behavior | Best for |
|---|---|---|
| Duplicates allowed | Each draw is independent; repeats can appear | Dice-style rolls, simulations |
| No duplicates | Each value appears at most once per run | Raffle winners, unique assignments, sampling |
How Often Duplicates Actually Happen
Repeats are more common than intuition suggests. Drawing 10 numbers from 1 to 100 with replacement carries about a 37% chance of at least one duplicate — the same birthday-paradox math behind shared birthdays in a classroom. If repeats would ruin the draw (two winners for one prize), always run with duplicates off.
Worked Example: Picking 3 Winners from 250 Tickets
Set Min to 1, Max to 250, Count to 3, and duplicates off. The generator might return 87, 12, and 203 — three distinct tickets drawn in one click, each with an equal shot. Because the range (250 values) far exceeds the count (3), the draw completes instantly. The history panel keeps your last 5 runs on screen, so you can re-check a result before announcing it.
The Range Limit
Asking for more unique integers than the range holds is impossible — 101 unique numbers cannot come from 1 to 100 — and the generator will tell you so. Widen the range or lower the count and run again.
Frequently Asked Questions
Why does the range need to be bigger than the count?
Unique draws remove each number from the pool. You cannot draw 20 distinct integers from a range that only contains 15, so the tool requires range size to be at least the count.
Can I shuffle a list of numbers this way?
Yes — set the range to 1 through N with Count equal to N and duplicates off, and you get a random ordering of every value, a true shuffle.
Does no-duplicates mode change the odds?
Slightly, in a good way for fairness: once a number is drawn it cannot win again, so late draws pick from a shrinking pool — exactly like physical ticket draws.
Can decimals be unique too?
Yes. In decimal mode the tool tracks each generated value to six decimal places and rejects repeats, though collisions are already rare in a continuous range.