Part III: Business & Regulation · Gambling Mathematics & Probability

74. La Partage / En Prison

Table Game Math

La Partage and En Prison are player-favorable rules available in French roulette and some European roulette games that reduce the house edge on even-money bets (red/black, odd/even, high/low) from 2.70% to 1.35%. Under La Partage (“the sharing”), when the ball lands on zero, players with even-money bets lose only half their wager instead of the full amount. Under En Prison (“in prison”), when zero hits, the even-money bet is “imprisoned” for the next spin — if the bet wins on the next spin, the original wager is returned (without winnings); if it loses or zero hits again, the wager is lost. Both rules have the same expected value mathematically, but La Partage is more common in practice because it resolves immediately. Macau’s VIP rooms and some Asian properties occasionally offer these rules to attract high-limit roulette players.

In practice

With La Partage, the house edge on even-money bets is exactly half the standard edge (1.35% vs. 2.70%). This makes French roulette with La Partage the best standard roulette bet available in most jurisdictions. The En Prison rule with single imprisonment has the same expected value as La Partage. Some French casinos offer double or triple imprisonment, which has marginally different expected values.

One entry from the Casino Industry Glossary — 1,157 terms written for surveillance, compliance and operations professionals rather than for players. Definitions describe industry usage; where a term carries a regulatory meaning, verify against the instrument that governs your jurisdiction.