Gambling terms, explained straight

Casino & Table Games

En prison roulette

En prison is a French roulette rule for even-money bets where a zero does not settle the wager immediately; instead, the stake is held over for the next spin.

Applies to
Even-money outside bets (red/black, odd/even, low/high) on single-zero roulette tables12
House edge
On a single-zero wheel, en prison reduces the house advantage to about 1.35%–1.38% for 1:1 bets34
Also called
Imprisonment; related to but distinct from la partage23

Key points

  • If the ball lands on zero, the even-money bet is not lost immediately; the stake is marked and held for the next spin.12
  • If the next spin wins, the stake is returned with no winnings; if it loses, the stake is forfeited.12
  • En prison differs from la partage, where the player loses only half the bet on zero, and from standard roulette where the full stake is lost.12

Where this term is used

Casino games Roulette wheel Describes the physical wheel and its numbered slots, including single-zero and double-zero variants. Casino games Roulette table Covers the layout of the betting area and the different types of roulette tables. Casino games Roulette odds Explains the probabilities and payouts for various roulette bets. Casino games Roulette bets Lists and defines the different types of bets available in roulette. Casino games Roulette wheel gambling Discusses the general activity of gambling on roulette wheels. Casino games Funny craps slang for numbers Funny craps slang for numbers are the colourful

Sources

  1. En prison - Wikipedia en.wikipedia.org Provides the core definition and explanation of the en prison rule.
  2. Roulette Basics – Rules, Bets, and Game Variations ... wizardofodds.com Confirms the rule's application to even-money bets and distinguishes it from la partage.
  3. Roulette en.wikipedia.org Supplies the house edge range of 1.35%–1.38% for en prison on single-zero wheels.
  4. Long-term behavior of casino games arxiv.org Gives the house advantage figure of 1/74 (≈1.351%) under the en prison rule.

Sources are drawn from regulators, universities and published research, and each one is labelled with what it actually is — a preprint is not called a paper. Bookmaker and affiliate pages are never cited here, because a page that sells betting is not a neutral authority on it.

Written and maintained by Ellis Warrender, writer and maintainer.

Last updated 28 July 2026. Spotted an error? Tell me and it gets fixed and logged on the corrections page.