How the wheel picks a winner
When you press Spin the wheel, the winner is chosen first and the animation comes second. The tool asks your browser’s cryptographic random number generator (crypto.getRandomValues) for a number and turns it into a slice. It uses rejection sampling, which throws away the rare values that would make some slices slightly more likely than others. Then it works out how far the wheel must turn so the pointer stops inside the winning slice, and plays a smooth spin that slows down over about five seconds.
The exact stopping point is random too, but it is always well inside the slice, never on the line between two names. What you see always matches the result.
Every line in the list is one slice, and every slice has the same chance:
Worked examples
A class of 25. Each student has 1 ÷ 25 = 4% chance on any spin. If you spin five times and allow repeats, the chance that one particular student is picked at least once is 1 − 0.96⁵ ≈ 18.5%. Tick Remove the winner after each spin and it rises to exactly 5 ÷ 25 = 20%, because nobody can be picked twice.
A weighted draw. Four people entered, but Ana bought two raffle tickets, so she goes on two lines: Ana, Ana, Ben, Cleo, Dev. That is five slices, so Ana has 2 ÷ 5 = 40% and the others have 20% each.
Choosing a presentation order. Put the whole group on the wheel, tick Remove the winner after each spin, and keep spinning. Each winner comes off before the next spin, so you build a full order with no repeats, and every possible order is equally likely. If you just want the order in one go, press Shuffle: it mixes the list with the same secure randomness.
Chance per spin
| Entries | Chance per spin | Picked at least once in 3 spins (repeats allowed) |
|---|---|---|
| 2 | 50% | 87.5% |
| 5 | 20% | 48.8% |
| 10 | 10% | 27.1% |
| 30 | 3.3% | 9.7% |
| 100 | 1% | 3.0% |
The last column uses 1 − (1 − 1/n)³, where n is the number of entries. Notice how fast the chance of being left out shrinks as the list gets shorter.
Picking without repeats
With Remove the winner after each spin ticked, the winner stays on the wheel when the spin ends, so everyone can see where the pointer stopped. The name is taken off just before the next spin. You can also press Remove under the result to take it off straight away, whether or not the box is ticked.
The history list under the tool keeps your last 100 results, numbered, with the time of each spin. It lives only in this page, so it disappears when you clear it or close the tab.
Sharing a wheel
Copy share link creates an address that rebuilds the same wheel on any device. The names are stored after the # in the link, in a compact encoded form. Browsers never send that part of an address to a web server, so the list is not stored on ours; it only travels to the people you send the link to.
Long lists make long links. For a classroom screen or a poster, turn the link into a scannable code with the QR code generator, and anyone with a phone can open the same wheel.
Tips
- Paste a column from a spreadsheet. Each cell lands on its own line. Spaces at the start and end are trimmed, and blank lines are skipped.
- Watch for duplicates. A name typed twice has double the chance. Press Sort A–Z to bring repeats next to each other so they are easy to spot.
- Big lists work. The wheel takes up to 500 entries. Above 50, the slices get too thin for labels, so the wheel shows colours only and the winner appears in large text below it.
- Reduced motion is respected. If your device is set to reduce motion, the wheel jumps straight to the result instead of spinning.
- Keep a record for prizes. Spin in front of the group or record your screen, and check any rules for promotions where you live.
Need a number instead of a name? Use the dice roller, which lets you roll anything from a coin-like d2 to a d1000. The same kind of secure randomness also powers the password generator.