Expected value is a way to work out if a free spins or any other type of casino bonus is financially worthwhile or not, and can be calculated using a formula that contains three variables; maximum bonus, wagering requirement and game house edge.
Consider, for example, a free spins bonus that can be played on a slot game with a house edge of 2.5%, with a wagering requirement of $2,000 (20x $100) and from which you can bank a maximum of $100:
EV of bonus = (maximum bonus) – (wagering requirement) x (game house edge)
EV of bonus = (100) – ($2,000) x (2.5%)
EV of bonus = (100) – ($50)
EV of bonus = $50
According to the formula, this free spins bonus has an EV of +$50 which means it’s definitely worth claiming. (If it had a -$50 EV, it would NOT be worth claiming).