How to calculate what a welcome bonus is really worth
Start with the turnover required: bonus amount multiplied by the wagering requirement. A €200 bonus at 35x requires €7,000 in bets. Then apply the house edge of the games you can play. On a slot with 96% RTP you lose on average 4% of turnover, so €7,000 of bets costs about €280 in expected losses, more than the €200 bonus. The bonus is still worth taking if you would play anyway, but do not mistake it for free money.
Low-wagering bonuses (bet365 at 20x) and no-wagering offers (PlayOJO) flip this calculation in your favour. Free spins with no wagering have a clear cash value: 50 spins at €0.10 on a 96% RTP slot are worth around €4.80 in expected return, all of it withdrawable.
Expiry is the silent killer. A 7-day window on a multi-thousand-euro bonus is designed for high-volume players; casual players will forfeit the bonus and any winnings from it.
Terms that catch players out
Maximum bet rules: most bonuses cap bets at €5 per spin while bonus funds are active. Exceeding this, even accidentally, can void all winnings.
Game weighting: slots usually contribute 100%, but table games, live casino and some high-RTP slots contribute 10% or nothing. Playing the wrong game means your wagering does not progress.
Maximum cashout: some bonuses cap the amount you can withdraw from bonus winnings. This is common on no-deposit offers and less so on deposit matches, but always check.
Sticky vs non-sticky: a non-sticky (or "parachute") bonus lets you play with real money first and only touches the bonus if you lose your deposit. This is far more player-friendly.