- Maths reviewed by Josh Miller
- Tested by Diana Westfield
The gamble feature on a slot offers to double your win if you guess a card’s colour. A gamble feature calculator shows the price of saying yes. Take a £20 win to the red-or-black gamble three times: the free CasinoCalcs calculator above says you’d walk away with £160 just 12.5% of the time, and with nothing the other 87.5%. On a fair gamble the average stays at £20. You don’t lose money on average, you swap a sure £20 for a long shot.
Gamble feature calculator: the odds of each round
| Gamble | Chance | Pays | Edge |
|---|---|---|---|
| Colour (red or black) | 50% | ×2 | 0% |
| Suit | 25% | ×4 | 0% |
| Colour, three times in a row | 12.5% | ×8 | 0% |
| Suit, twice in a row | 6.25% | ×16 | 0% |
Each round is independent, so the chance of n wins in a row is the single-round chance to the power n. A red card last time doesn’t make black more likely next time.
When the gamble does cost you
The classic card gamble is fair. Some ladder gambles, wheel gambles and newer “risk” features aren’t: they pay less than the odds, for example a 50% climb that only adds 1.8× instead of 2×. Choose “Ladder or custom” and enter the chance and multiplier to see the edge. A 1.8× pay at 50% has a 10% edge on every step, which compounds: three steps keep 27% of the original value.
Many UK online slots have no gamble feature at all now, and some remove it for players in certain countries. If yours has one, it’s purely a question of how much risk you want, not how much you win on average. For the wider picture on a session, the slot bankroll calculator shows how long your money lasts, and the chasing losses calculator does the doubling maths for winning back a loss.
Play for fun with money you won’t miss. If you’re spending more than you planned, BeGambleAware.org is free and confidential.