Independent site. CasinoCalcs is not affiliated with or endorsed by any lottery, raffle or prize competition operator. Game names are used only to describe the rules the maths is based on.
- Maths reviewed by Josh Miller
- Tested by Diana Westfield
A competition odds calculator is worth having before you buy 20 tickets for a car or a cash prize. The sums are simple: your tickets ÷ tickets sold. Ten tickets in a 4,999-ticket draw that sells out is about 1 in 500. The free CasinoCalcs calculator adds the part the listing doesn’t show, which is how much of your money comes back on average and what the operator keeps.
Odds of winning a competition, in real numbers
Here’s a typical online prize draw: 4,999 tickets at 99p, prize £2,500 cash alternative.
| Tickets you buy | Cost | Chance if it sells out | Expected value |
|---|---|---|---|
| 1 | £0.99 | 1 in 4,999 | −£0.49 |
| 10 | £9.90 | 1 in 500 | −£4.90 |
| 50 | £49.50 | 1 in 100 | −£24.50 |
| 250 | £247.50 | 1 in 20 | −£122.47 |
Notice the expected value scales with the tickets. Buying more lifts your chance in a straight line and your average loss in exactly the same line. There’s no bulk discount on the maths.
The number that matters: the margin
Sales of £4,949 for a £2,500 prize leaves a margin of about 49%. That’s normal for this kind of competition, and far higher than a casino game. If a listing says “only 999 tickets” for a £10,000 prize at £5, the fair price is £10.01 and the odds are on your side, assuming it sells out. Run it here before you believe it.
Competitions that stall short of selling out change the picture. If only 60% of tickets go and the draw still happens, each ticket is worth more. Some operators extend the deadline instead, or switch to a lower cash prize. The rules page tells you which.
Giveaways, sweepstakes and postal entries
Free giveaways work the same way: your entries ÷ all entries. The only difference is that it costs nothing, so the expected value is positive however poor the odds. The free postal route on a paid competition is the same idea. For draws with several prizes, the raffle odds calculator handles them one prize at a time, and the tombola odds calculator covers the fête version.
Buying more tickets to chase a prize is how a hobby turns into a habit. BeGambleAware.org can help if that sounds familiar.