Enter the weights and the real odds appear
Type one item and weight per line and the page works out each item's odds as its own weight divided by the total, then prints them in the table. Add a number of repeat spins and it places the expected count, which is the odds times the spins, next to the count actually observed over that many spins, with the gap between them. The point is not simply to receive one result from a set of weights but to check whether the odds you set really come out that way.
Assumptions and what is not covered
Each spin is assumed independent and the weights unchanged between spins. Drawing without replacement, entering a reward per item to compute an expected value, and any spinning wheel animation are not covered. The expected count is a long run average, so do not read it as projected profit or a guaranteed outcome. No published threshold was found for how wide a gap between observed and expected counts would mean the setup is wrong, so the page shows the gap without ruling on it. The browser Math.random function is not a cryptographically secure random source, so do not use it for draws that carry legal weight or money. Up to 100 items and 100,000 spins are handled. Written as of October 2026.
Frequently asked questions
A weight is a ratio, so on its own it is not a percentage. Each item takes its own weight divided by the total, so with weights of 5, 3, 2 and 1 the total is 11 and the 5 works out at 45.45%. The table shows that figure for every item.
The expected count is the odds times the number of spins, a long run average, while the actual count comes from one run. With a finite number of spins the two normally differ, and the gap tends to shrink in relative terms as the spins increase.
That item sits at 0% and is never drawn. If every weight is 0 the total is 0 and no draw is possible, so the page shows a notice and stops.