Expected value in betting

Expected value is the average result of a bet if you could repeat it endlessly. Positive EV means the bet makes money in the long run; negative EV means it loses, however it turns out this time.

Weigh each outcome by its probability and add the results. The number you get is per-bet profit expressed in your stake currency, and it is the only measure that survives a bad weekend. EV thinking also explains why bonuses, boosted prices and free bets are worth taking even when they lose: their expectation is positive at the moment of placement.

EV = Σ (probability of outcome x profit or loss of outcome).

A ₦2,000 bet at 3.20 on a 35% chance: EV = (0.35 x ₦4,400) - (0.65 x ₦2,000) = ₦1,540 - ₦1,300 = ₦240 per bet, a 12% return on stake. Place that bet weekly for a year and the expectation is roughly ₦12,480 profit, with swings of several times that in both directions along the way.

It converts betting from a results business into a process business. Judging yourself by EV rather than by last weekend's P&L is the difference between a strategy and a mood.

Deposit bonuses and free-bet offers common on Nigerian sites are usually the highest-EV bets available to a small bankroll — provided you read the rollover terms, which frequently turn a positive-EV headline into a negative-EV product.

• Calculating EV from a probability you invented five seconds earlier.
• Ignoring the variance around a positive EV and staking too heavily to survive it.
• Assuming a positive-EV free bet is still positive after a 5x rollover at minimum odds of 3.00.