Guru Gwen
11 Jan 2022
•
18 min read
Casino bonuses look generous on the surface:
“Deposit $/€100, get $/€300 FREE! Play with $/€400!”
But here’s what they don’t tell you:
How is this legal?
Because the math is technically disclosed — it’s just buried in terms and conditions written to confuse you.
This guide decodes the mathematics behind casino bonuses so you understand exactly what you’re signing up for.
Every casino bonus is built on three mathematical concepts:
Let’s break each down.
House Edge = The casino’s mathematical advantage
Every casino game is designed so that, over time, the casino profits. This advantage is called the house edge.
Examples:
What it means:
If you wager $/€100 on a game with a 4% house edge:
Key insight:
The house edge applies to every dollar wagered — not every dollar you deposit.
RTP = House Edge’s opposite
RTP is the percentage of all wagered money a game returns to players over time.
Formula:
RTP = 100% − House Edge
Examples:
Important: RTP is calculated over millions of spins or hands.
In any single session:
This is variance. Short-term results swing wildly. Long-term results converge on the RTP.
Here’s where bonuses become traps.
Example Bonus:
Step 1: Calculate total playthrough
40x ($/€100 + $/€100) = $/€8,000 must be wagered
Step 2: Calculate expected loss
Assuming 96% RTP slots (4% house edge):
$8,000 × 0.04 = $/€320 expected loss
Step 3: Calculate net value
Net result: −$/€120
You’re expected to lose $/€120 completing this bonus — even though you started with $/€200.
Here’s the formula to calculate any bonus’s true value:
True Bonus Value = Bonus Amount − (Total Wagering × House Edge)
Example 1: Bad Bonus
You lose money claiming this bonus.
Example 2: Good Bonus
This bonus has positive expected value. You’re expected to come out $10 ahead.
Not all games count equally toward wagering.
Typical contribution rates:
What this means:
If you have $/€1,000 wagering to complete:
The trap:
Casinos promote bonuses for slots because slots:
Casino Offer:
“500% MATCH BONUS! Deposit $/€100, play with $/€600!”
Terms (in small print):
Step 1: Total wagering
60x ($/€100 + $/€500) = $/€36,000
Step 2: Expected loss
$/€36,000 × 0.04 = $/€1,440 expected loss
Step 3: True value
$/€500 − $/€1,440 = −$/€940
You’re expected to lose $/€940 claiming this “500% bonus.”
Step 4: Time required
Step 5: Probability of completion
With an expected loss of $/€1,440 and only $/€600 starting balance, you will almost certainly bust before completion.
Verdict:
This bonus is a mathematical trap designed to look generous but extract maximum value.
Good bonuses share these traits:
Example of a GOOD bonus:
You’re not profiting, but you’re getting double the playtime for the same expected loss.
Offer: “$/€25 free, no deposit required!”
Reality:
The math:
You’re expected to lose more than the bonus itself.
The real purpose:
Treat these as free trials — not profit opportunities.
Rather than calculating manually, use the BetEdge Bonus Value Calculator.
It shows:
[Try the Bonus Value Calculator →]
Before claiming any bonus, ask:
If you answer no to any, skip the bonus.
Casino bonuses aren’t gifts — they’re marketing tools.
The math is always in the casino’s favor. The only question is by how much.
Sometimes the best bonus is no bonus at all.