A weight is a number of chances. Weight 3 means that entry sits in the draw three times over, so on a list of Jamie (1), Alex (3) and Sam (1), Alex wins about sixty per cent of the time — three of the five total chances.
Adding weights by hand
In the names box, put a star and the number after the name:
- Jamie
- Alex *3
- Sam
A name with no star keeps one chance, and a star with no number after it is just part of the name, so “Alex * the great” stays intact.
Adding weights from a spreadsheet
During import, choose a weight column — a bonus entries column, a ticket quantity, a multiplier. Blank, zero, negative and unreadable values all become one chance. Dropping somebody from a draw because a cell was empty is not a decision to make silently.
People and chances
When weights are on, the count under the wheel shows both: “482 entries · 637 total chances”. The first is how many people are in the draw. The second is how many chances exist between them.
Why the wheel does not repeat a name
A name with twenty chances would take twenty slices and make the wheel unreadable. Spinnza shows the entry once and applies the weight to the draw, which is exact either way.
What the draw does with the numbers
Chances are whole numbers, and the draw adds them into a running total and picks a position in that total with a single random integer. Nothing is multiplied, divided or rounded, so there is no drift that accumulates across a long list — a weight of 3 in a total of 637 is exactly three 637ths, on ten entries or on ten thousand.
That integer comes from the browser's cryptographic random source, reduced to the range by discarding out-of-range draws rather than by taking a remainder. Using a remainder would make the lowest few positions very slightly more likely, which nobody would ever notice and which would still be wrong.
Choosing weights people will accept
The maths works at any ratio. The promotion does not. Two rules keep weights defensible:
- Keep the spread small enough to explain in a sentence. “Follow is one entry, share is two, tag a friend is three” is a rule. A range from 1 to 50 is a negotiation.
- Publish the weights with the rules, not after the draw. A weighting nobody knew about looks like one invented to fit the winner.
There is also a readability limit. Three chances is obvious on the wheel; fifty is a wall of one colour, and the picture has stopped doing its job even though the draw is still exactly right. If one entry is worth fifty of another, it is worth asking whether they belong in the same draw.
A weight is not a promise
This is the part that causes complaints. Sixty per cent odds lose four times in ten, and on a small list an unlikely outcome is not just possible but ordinary — the entrant with triple chances will sometimes lose to somebody with one, and that draw was not broken. If an entrant is supposed to be certain to get something, that is not a draw at all: give them the prize and draw for the rest.