La partage and en prison change zero settlement on eligible even-money wagers: red/black, odd/even and low/high under the applicable rule. Dozens, columns and inside bets do not automatically receive that treatment.
La partage settles a half loss
With 10 chips on red, red wins 10 profit and black loses 10. Under la partage, zero returns 5 and loses 5. The round ends with half the original wager lost.
On a fair single-zero wheel, expected profit per chip is:
18/37 × 1 + 18/37 × (−1) + 1/37 × (−0.5) = −1/74.
The house edge is about 1.35% on that eligible wager. The calculation assumes that exact half-loss rule and standard even-money payouts. It does not reduce the edge of a straight-up wager or dozen.
En prison leaves a barred wager
An en prison procedure keeps the original stake barred after zero. A favorable later resolving result recovers the stake without normal winning profit. A contrary resolving result loses it. Monte-Carlo's published rule offers division or waiting for another spin.
Scroll to compare all columns
| A 10-chip red wager | Settlement in the described procedure |
|---|---|
| Red first | 10 profit plus original 10 returned |
| Black first | 10 lost |
| Zero, then red | Original 10 recovered without profit |
| Zero, then black | Barred 10 lost |
| Zero, then zero | Apply the table's repeated-zero rule |
Recovered stake is not profit. While barred, the wager is unavailable for another selection.
State the repeated-zero assumption
If a model keeps a wager imprisoned through repeated zeros until red or black resolves it, conditional recovery has probability one half. That assumption produces the same 1/74 expected loss per original unit as la partage. A rule that loses the barred stake on the next zero produces a different expectation.
Read the exact rule rather than quoting one reduced edge for every en prison game. The house-edge guide explains expected-value weighting; French roulette separates vocabulary from settlement. The calculator uses ordinary full-loss-on-zero assumptions unless its displayed controls state otherwise.
Sources and scope
- Roulette probability derivation. Amenti Labs LLC. Fair independent pockets, fixed payouts, full outside loss on zero. Formula and all supported bets regression tested.
Publication date: 2026-11-07. Checked 2026-11-07.
- European Roulette: rules of the game. Monte-Carlo Société des Bains de Mer. Published venue European roulette rules:37 pockets, wager names/payouts including firstfour, evenmoney zero division/barredstake choices and prohibition on spokenbets. Does not establish universal French game rules or a repeatedzero policy. Reducededge figures are separately scoped mathematical derivations.
Publication date: not stated. Checked 2026-11-08.