🎡 Spin the wheel — who's paying?
Put everyone in the draw, say what the winner owes — the pizza, the beers, the next round — then give it a spin. The wheel stops on one of them and that is the decision, so no arguing and no volunteers.
The wheel
Why use this wheel?
Some decisions are not worth an argument, and who is paying for the pizza is the classic one: somebody feels put upon, somebody never volunteers, and the fairest way to settle it is the one nobody proposes. This wheel gives every name in the draw the same chance and settles it in front of everybody, in one spin. It also makes the answer hard to argue with, which is most of the point.
How random are we, really?
This wheel is only as fair as the draw behind it, and randomness itself is stranger than it looks:
- The birthday paradox: 23 people in a room are enough for it to be more likely than not that two of them share a birthday, because 23 people make 253 pairs to compare. Coincidences multiply faster than intuition expects, which is most of the reason a fair draw can still feel rigged.
- A coin toss is not exactly 50/50. Research into the physics of the toss finds a coin slightly favours the side that was facing up when it was flipped, because a flipped coin keeps a little of the orientation it started with.
- RAND published a book of random numbers, A Million Random Digits with 100,000 Normal Deviates, in the 1950s. The digits came from an electronic simulation of a roulette wheel and were then filtered and tested for bias — a breakthrough at the time, since the largest table published before it was a tenth the size. Published tables have one flaw for anything secret, though: anyone can look them up.
How does this wheel pick a winner?
The winner is drawn first, at random, and the wheel is then aimed so that it stops inside that name's wedge:
winner = the name at floor(random × the number of names)
Every name gets an equal wedge of the circle — one row in the form is one wedge — so nobody is weighted and there is nothing to rig.
- The spin adds four to six whole turns to whatever the wheel has already turned, plus the part-turn needed to bring the winner's wedge under the pointer.
- The pointer is aimed well inside the winning wedge rather than at its edge — at least 12% of a wedge away from the line on either side — so a landing never looks like a coin toss between two names.
- The rotation only ever grows, which is why the wheel always travels the way a wheel should instead of snapping backwards.
- The spin is animation; the draw is the arithmetic above. Spinning first and reading the pointer afterwards would come to the same answer, but only this way round can the landing be promised.
- A long name is shortened inside its wedge (the whole name is always the one printed under the wheel), and past nine names the writing steps down a size to fit.
Frequently asked questions
Is it really random?
The name is drawn with the browser's own random number generator, which is the same source any ordinary online draw uses and is more than good enough for the pizza. It is not cryptographic randomness — nothing a browser can produce is — so treat it as fair rather than tamper-proof, and do not use it to decide anything that has to stand up to a lawyer.
Is the result decided before the spin starts?
Yes, and the page has never pretended otherwise: the winner is drawn first and the spin is aimed at it. Spinning the wheel and then reading where the pointer stopped would give the same answer, and this way round the pointer can be kept clear of the line between two wedges, so a landing never has to be argued over.
Can the same person win twice in a row?
Yes. Every spin is independent, so winning once neither uses up anybody's luck nor makes a second win less likely. Two pizzas in a row is a 1-in-16 event with four people in the draw, which is uncommon rather than impossible, and the wheel is not cheating when it happens.
How many names can go in the draw?
Two to twelve. Fewer than two is not a draw — there would be nothing to decide — and past twelve the names stop fitting in their wedges even at the smaller writing, so a longer list is better settled by two rounds than by one crowded wheel.
What decides the winner — the wheel or the list?
The list. One row is one wedge, and every wedge is the same size, so the draw is only as fair as the names you put in: adding somebody twice gives them two chances, and removing a name takes that chance away. If the same person is winning more often than they should, count the rows.
Does it work without JavaScript?
No. The wedges and the names in them are drawn by the script, and so is the spin, so with scripting turned off there is nothing to turn. Every other page on this site keeps working without it, since they are only arithmetic — this one is the exception.
Can I use it for something other than who pays?
Yes. The box under the chips takes any sentence you like — who empties the dishwasher, who picks the music, who drives — and the chip you choose is only a shortcut for filling it in. The wheel's job is to point at somebody; what they owe is whatever you typed.
What does the share button actually send?
The sentence on the line under the wheel and a link to this page, and nothing else. The site sends nothing anywhere by itself: the button hands that sentence to your own device’s share sheet, or puts it on your clipboard when the device has no share sheet to offer. What you do with it after that is between you and whichever app you picked.