Casino bonus EV explained
By Dana Reeves, Lead Bonus Analyst · Updated 2026-06-23
'Expected value' (EV) is the one number that tells you whether a casino bonus is actually worth claiming. It is the average amount you would keep (or lose) if you cleared the same offer many times. This guide shows the formula, why the headline percentage is misleading, the factors that move EV, a full worked example, and how to read any offer in under a minute.
The formula
EV = Bonus − (Bonus × Wagering × (1 − RTP)). With RTP assumed at 0.96, a $200 bonus at 35x = $200 − ($200 × 35 × 0.04) = $200 − $280 = −$80. Negative EV means that, on average, you expect to lose money clearing the bonus — the wagering costs more than the bonus is worth.
Why the headline percentage is misleading
A '300% up to $600' bonus sounds far better than '100% up to $200', but the match size barely matters once wagering is applied. What decides EV is the combination of bonus size, wagering multiplier, game RTP and max cashout. A smaller bonus at 10x routinely beats a huge one at 45x. Operators lead with the percentage precisely because it is the least informative number.
RTP and variance
RTP is the long-run return of a game; 96% is a common slot baseline. Higher-RTP games clear wagering more cheaply. Variance is separate — it's the swing around that average. Low EV with high variance means you'll occasionally win big but usually lose; positive EV is what makes the bet worth taking at all. EV tells you whether to play; variance tells you how bumpy the ride is.
Game contribution changes the real EV
If table games contribute only 10% to wagering, clearing the bonus through them multiplies your turnover — and therefore your expected loss — roughly tenfold. Always compute EV using the games you'll actually play at their real contribution rate, not the slot assumption.
Max cashout caps your upside
Many bonuses cap how much you can withdraw from bonus winnings (e.g. 5× the bonus). That cap truncates the good outcomes while you still bear all the downside, which lowers true EV below the simple formula. If a bonus has a tight max cashout, treat the headline EV as optimistic.
Read any bonus in a minute
1) Find the bonus amount and wagering multiplier. 2) Multiply them to get required turnover. 3) Take ~4% of that turnover as expected loss (at 96% RTP). 4) Compare it to the bonus: if the loss exceeds the bonus, skip it. For an exact figure that accounts for your numbers, use the free EV calculator.
When a bonus IS worth it
Positive-EV offers do exist: low or zero wagering, cashback/rakeback paid as real cash, no-deposit bonuses, and high-RTP-eligible promotions. These are worth claiming. The point of EV is not to avoid all bonuses — it's to claim the good ones and skip the traps.
See it applied
Every BonusOz review shows this calculation for that casino's specific offer, plus a clear claim-or-skip verdict. Start with the lowest-wagering options in our wagering guide.