En Prison Rule: Definition and How It Works in Roulette

The En Prison rule applies only to even-money outside bets: red/black, odd/even, and high/low. When a player places one of these wagers and the ball settles on zero, the bet is not lost immediately. Instead, the croupier marks the chips as “imprisoned,” leaving them exactly where they sit for the next spin. A win on that following spin returns the full original stake with no extra payout; a second loss forfeits the entire amount. The rule originated in French casinos and remains a defining feature of French roulette tables, setting them apart from standard European and American layouts that resolve zero spins as an outright loss for even-money bets.

How a Prisoned Bet Resolves

Picture a player staking CAD 20 on red. The ball lands on zero, so the croupier places a marker on the chips rather than collecting them. On the next spin, if red appears, the player recovers the full CAD 20; if black or zero appears again, the stake is forfeited. Some tables apply a double prison rule when zero repeats, locking the bet for a further spin instead of an immediate loss, which slightly extends the recovery window while keeping the underlying odds unchanged.

On a single-zero wheel, the standard house edge on even-money bets is 2.70%. The En Prison rule cuts this to approximately 1.35%, roughly halving the operator’s mathematical advantage on red/black, odd/even, and high/low wagers. This reduction happens because the rule effectively returns a portion of expected losses back to the player over repeated zero outcomes, even though a single imprisoned bet either wins back in full or is lost entirely. Canadian players comparing roulette variants at licensed online casinos should note this edge only applies to outside even-money bets and not to inside bets on single numbers, columns, or dozens.

Live dealer platforms and RNG-based French roulette tables that advertise the En Prison option typically disclose it directly in the game rules or paytable. Players should always confirm the rule is active before relying on it, since some European roulette tables omit it entirely and instead apply a straightforward loss on zero for all bet types.