£100
isn’t £100.
The headline is advertising. The terms are the product. See what a casino bonus is mathematically worth before you touch it.
Run the numbersSame offer. Different truth.
01 / INPUT
Build the offer
Change any term. The analysis updates as you type.
Check the game’s info screen. Operators can run different RTP versions of the same slot.
Some offers only count a fraction of each slot bet toward the wagering requirement.
Affects how wide the range of outcomes is. It does not change the average return per spin, which is set by the RTP, but a more volatile slot runs a balance down more often.
02 / ANALYSIS
Your expected value
Expected Value
+£60.00
Positive expected value
If you complete the wagering. That means staking £1,000 in total.
Played once from a £110 balance at £0.55 a spin
Average outcome +£65.99. Most likely outcome −£10.00, with 55% of attempts finishing with nothing. Middle 80% of outcomes: −£10.00 to +£219.89.
This differs from the figure above because that one assumes you see the wagering through. A single attempt stops when the balance runs out, and you cannot lose more than you put in.
Expected value is an average across many outcomes, not a prediction of yours.
18+ only. If gambling stops being fun, free confidential help is at BeGambleAware.org.
Breakdown
Live terms simulator
Weighting matrix
One £100 bonus. One 10x wagering rule. One 96% RTP slot. Choose the contribution rate to see how a small term changes the result. Illustrative only.
Full contribution keeps the play-through shortest.
Frequently asked questions
What is expected value on a casino bonus?
The average amount a player ends up with across many attempts at the same offer. A £100 bonus at 10x wagering on a 96% RTP slot needs £1,000 of stakes. At a 4% house edge that costs about £40, so the offer is worth roughly £60, not £100. It is an average, not a prediction of any single attempt.
Why does game contribution matter more than the wagering number?
Since January 2026 a UK-licensed operator cannot set wagering above 10x the bonus, so the headline multiple varies far less than it used to. Contribution did not change. If the eligible slots contribute 25%, the same £100 bonus at 10x needs £4,000 of stakes rather than £1,000, which costs about £160 and turns a £60 offer into a £60 loss. Same headline, opposite answer.
Where do I find the RTP and the contribution rate?
RTP is on the game's own info screen, not on a review site: operators can run different RTP versions of the same slot. Contribution is in the bonus terms, usually well below the headline, and it is the number most people never check.
Why does the calculator say most attempts finish with nothing?
Because they do, and an average hides it. The average is carried by a small number of large wins, so the middle outcome sits far below it and is often zero. How often depends on the slot's volatility and how much you stake per spin, which is why both are shown alongside the figure.
Can I lose more than I deposit?
No. Your deposit is the most you can lose on a single attempt. That also means a negative expected value does not appear as a bigger loss on screen: it means the offer costs you more to clear than the bonus is worth, over many attempts.
Guides
Safer gambling / practical controls
The best outcome can be not playing.
A calculator can explain an offer. It cannot make gambling risk-free. Set limits while the decision still feels easy, and stop if gambling is affecting your money, time or wellbeing.