Bonus bet calculator: how to work out what a bonus is really worth
One simple formula turns any casino bonus or bonus bet into a single honest number you can compare.
The headline on a bonus tells you how much you get. It doesn't tell you what it's worth. A bonus bet calculator answers that second question, and you can do the same sum by hand: you need the bonus, the wagering and the game's RTP (or, for sports, the bookmaker's margin).
The bonus value formula
Each part comes from a different line of the terms:
- Bonus: the amount added to your account.
- Total to bet: bonus × wagering, or (deposit + bonus) × wagering if the terms say so. Our wagering requirements guide explains the difference.
- House edge: 100% minus the game's RTP. Slots at 96% RTP have a 4% edge.
A worked bonus calculation at 45× wagering
Say you deposit $100 and get a 100% bonus at 45× wagering, playing slots at 96% RTP.
- Bonus: $100
- Total to bet: $100 × 45 = $4,500
- Expected cost of betting that: $4,500 × 4% = $180
- Real value: $100 − $180 = −$80
On average, taking this bonus leaves you $80 worse off than not taking it. The bonus looked like $100 and turned out to be negative.
The same bonus at 10× wagering
- Total to bet: $100 × 10 = $1,000
- Expected cost: $1,000 × 4% = $40
- Real value: $100 − $40 = +$60
Same deposit, same bonus, same game. The only thing that changed was the wagering, and the bonus went from a loss to a gain.
When the deposit counts too
Now take the 10× offer but with wagering on deposit + bonus. You must bet ($100 + $100) × 10 = $2,000. Expected cost: $2,000 × 4% = $80. Real value: $100 − $80 = +$20. Still positive, but a third of the bonus-only version.
How RTP shifts the answer
The same $100 bonus at 35× on a 97% RTP slot: $3,500 × 3% = $105, so the value is −$5. On a 94% slot: $3,500 × 6% = $210, so −$110. The game you pick can matter as much as the offer. See what RTP really means for where to find it.
Bonus bets on sports: swap RTP for margin
A sportsbook bonus works the same way, with the bookmaker's margin in place of the house edge. Take a $50 bonus with 5× rollover, betting into markets with a 5% margin:
- Total to bet: $50 × 5 = $250
- Expected cost: $250 × 5% = $12.50
- Real value: $50 − $12.50 = +$37.50
Free bets are different again, because you don't get the stake back, so they need their own formula.
What the formula leaves out
- Running out of balance. If your balance hits zero before you finish wagering, you stop. So with harsh terms the real average loss is capped by what you put in, and the formula can look worse than reality.
- Max cash-out and max bet rules. These can cut the upside or void the bonus. Check our guide to max bet, max win and expiry.
- Game weighting. If your game counts only 10%, multiply the total to bet by ten.
Don't want to do it by hand? Enter the offer in our bet calculator and it runs these steps for you.
Check your own bonus
Put any offer into the bet calculator and see its real value in seconds.