How to Calculate the True Cost of a Gambling Bonus
A worked framework for translating a headline promotion into required wagering action and theoretical game cost.
Calculate the requirement base × multiplier, adjust for game contribution, then estimate the theoretical cost of the required action using a rules-appropriate house edge. The result is an analytical benchmark—not guaranteed profit or loss.
Step 1 — calculate credited turnover
A $100 bonus at 20× bonus-only wagering requires $2,000 of credited wagering. If 20× applies to a $100 deposit plus $100 bonus, credited wagering is $4,000.
Step 2 — adjust for contribution
At 25% contribution, $2,000 of credited wagering requires $8,000 of actual action. At 100% contribution it requires $2,000.
Step 3 — estimate game cost
If the qualifying game has a 4% theoretical house edge, $2,000 of action carries about $80 of long-run expected game cost; $8,000 carries about $320.
Step 4 — inspect non-math restrictions
Expiry, max-bet rules, excluded games, maximum cashout and verification requirements can dominate the headline number.
Step 5 — account for variance and ruin risk
Even when bonus amount minus theoretical cost is positive, the player can lose the available bankroll before completing turnover. Expected-value arithmetic does not remove variance.