Methodology
This page explains how BonusWijs.nl calculates the expected value of casino bonuses and the assumptions involved. The explanation is technically accurate, but deliberately written in plain language.
what's here
The formula, default assumptions, worked examples, free-spin valuation, and where the model stops.
default assumptions
Published RTP, full playthrough, and a conservative read of caps, weighting, and cashout limits.
when this helps
Use this page when you want to understand where our EV scores come from before you compare offers yourself.
What is expected value?
The core of the site is expected value, EV for short. It tells you how much a bonus earns or costs you on average over the long run, expressed in euros. A positive EV means the bonus offers an advantage on paper, a negative EV means the bonus costs you money on average.
go deeper
The short definition lives here. The knowledge-base version walks through EV one bonus at a time.
Read the full article: What is EV? →The formula
In most cases a simplified but robust model is used:
core formula
EV = effective bonus − expected loss
Effective bonus
What you actually receive
Expected loss
Total wager × house edge
EV
Expected value of the bonus
This approach assumes a constant bet per spin and does not account for bonus features that change the variance. The result is a reliable estimate, not an exact prediction.
Read the full article: Wagering explained →Worked example
Negative EV
Casino X: 100% match up to €100, wagering 30×. No free spins. RTP 96%.
Step 1. Effective bonus: €100
Step 2. Total wager: 30 × €100 = €3,000
Step 3. Loss: €3,000 × 4% = €120
Step 4. EV: €100 − €120 = −€20
This bonus costs you €20 on average. High wagering eats up the bonus.
Positive EV
Casino Y: 100% up to €100, wagering 10×. 200 spins at €0.20. RTP 96.5%.
Step 1. Bonus: €100 + (200×€0.20×0.965) = €138.60
Step 2. Total wager: 10 × €100 = €1,000
Step 3. Loss: €1,000 × 3.5% = €35
Step 4. EV: €138.60 − €35 = +€103.60
This bonus gives €103.60 on average. Low wagering plus extra spins make it worth it.
The negative example is worked out step by step below:
Fully worked out (negative example)
Casino X offers: 100% match up to €100 plus 50 free spins. Deposit: €100. Wagering: 30× on bonus money. Free spin value: €0.10. Slot RTP: 96%.
- 1. Effective bonus€100 match bonus + (50 × €0.10 × 0.96) = €100 + €4.80 = €104.80
- 2. Total wager30 × €100 = €3,000
- 3. Expected loss€3,000 × (1 − 0.96) = €3,000 × 0.04 = €120.00
- 4. Expected value€104.80 − €120.00 = −€15.20
This bonus has a negative EV. You lose €15.20 on average.
The process in a diagram
Here is how a bonus flows through the model:
Deposit
€100
Bonus
+€100
Wagering
€3.000
in wagers
Balance
~€80
expected balance
Payout
€80
How free spins are valued
Not every free spin is equal. The value depends on:
| Factor | Example | Impact |
|---|---|---|
| Nominal bet | €0.10 vs €0.20 | Direct 2× value |
| Slot RTP | 94% vs 97% | Higher RTP = more value |
| Win cap | Max €20 in winnings | Caps expected value |
| Own wagering | 40× on winnings | Lowers net return |
Our formula
Value per spin = nominal bet × RTP × (1 − wagering loss)
Cashout limits
Some bonuses have a maximum payout (for example max 5× the bonus). That caps the upside of the variance.
Approximation
EV_capped = min(EV_uncapped, max_payout − deposit)
With very low cashout limits, a seemingly positive bonus can still come out negative.
Which RTP is used?
The calculation uses the RTP published by the casino for each game, not the provider's theoretical maximum RTP.
Dutch online casinos with a KSA licence must publish their RTP settings. These can be lower than the standard provider RTP.
Default assumption: If no specific RTP is available, the calculation uses 96.00% for slots and 98.50% for blackjack.
Table games and live casino
Separate RTP assumptions apply to table games and live casino: 98.50% for blackjack, 97.30% for roulette. In the calculator you can pick the game type.
What the model does and does not do
✅ Does
- Computes the mathematical expectation based on the bonus terms
- Accounts for wagering, RTP, free spins and cashout limits
- Uses casino-specific RTP where available
⚠️ Does not / simplified
- Does not account for player behaviour (raising bets, all-in)
- Assumes a constant bet per spin
- Does not model bonus features or per-slot variance
- Free spins tied to progressive jackpots are not valued separately
A conservative model is used on purpose: slightly too careful rather than too optimistic.
How is BonusWijs funded?
BonusWijs is a personal project with no revenue. There are no affiliate links, advertisers, sponsors or investors. The site runs on private funds. That keeps the calculations independent of commercial interests.
Sources and further reading
primary source
KSA: Rules for online gamblingRTP data comes from the individual casinos, as required by the KSA licence. Where casino-specific RTP is not available, the standard provider RTP is used.
The calculations are based on standard probability theory. The methodology is open and verifiable. Questions or corrections are welcome at info@bonuswijs.nl.
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