En Prison can reduce the effective house edge on qualifying even-money roulette bets to about 1.35%. When zero lands, the bet is not immediately lost. It is held “in prison” and settled according to the table rule, often giving the player a chance to recover the original stake.
Quick Facts
- En Prison usually applies only to even-money bets.
- It is most common on French or French-style roulette tables.
- The bet is held after zero instead of being fully collected.
- Under common treatment, the effective edge is about 1.35%.
- House rules matter, especially on repeat zero.
- It reduces cost but does not create a winning game.
- It is more procedural than La Partage and easier to misunderstand.
Plain Talk
En Prison means the bet goes to jail.
You place an even-money bet, such as red. The ball lands on zero. Instead of losing immediately, your bet stays on the table. The dealer marks or controls it according to the house procedure. On the next qualifying spin, the bet is resolved.
In many versions, if your side wins next, you get your original stake back but no profit. If your side loses, the stake is lost. If zero repeats, the rule may keep the bet imprisoned again or settle it another way, depending on the casino.
That last detail matters. En Prison is not one universal rule. It is a family of zero-settlement procedures.
The Wizard of Odds roulette basics gives the standard roulette house edge framework. Regulatory and approved-rule documents such as the Nevada roulette rules of play and Massachusetts roulette rules show why exact table procedure matters in roulette settlement.
For the player rule, read En Prison rule. For the simpler half-loss version, read La Partage rule.
How It Works
A simple En Prison sequence looks like this:
| Step | What happens |
|---|---|
| 1 | Player bets $20 on red. |
| 2 | Zero lands. |
| 3 | The $20 bet is held in prison. |
| 4 | Next spin decides the imprisoned bet under house rules. |
| 5 | If red wins, the player may receive the $20 stake back with no profit. |
| 6 | If red loses, the $20 stake is collected. |
Under the common recursive version, repeat zero keeps the bet imprisoned. That produces an effective edge close to La Partage.
| Rule | Zero result | Effective edge on even-money bets |
|---|---|---|
| Normal single-zero | Full loss | 2.70% |
| La Partage | Half loss | 1.35% |
| En Prison, common recursive version | Bet held for later resolution | About 1.35% |
| En Prison, zero loses on next spin | Bet held once, harsher repeat-zero treatment | Slightly above 1.35% |
The main lesson is simple: ask what happens after zero, and ask what happens if zero repeats.
Roulette Table Example
You bet $30 on even.
Zero lands.
The dealer says the bet is En Prison. Your $30 does not lose immediately.
Next spin lands on 24, an even number.
Under the common version, your $30 is returned. You do not win $30 profit. You just escape the zero.
Now compare long-run cost on $3,000 of even-money action:
| Rule | Total action | Approximate edge | Expected loss |
|---|---|---|---|
| Normal single-zero | $3,000 | 2.70% | $81.08 |
| En Prison, common treatment | $3,000 | 1.35% | $40.54 |
That is a real improvement. It is not a guarantee of a good night.
From the Casino Side:
En Prison is more demanding than La Partage because the dealer must track unresolved bets.
A half-loss is immediate. An imprisoned bet carries forward. That creates more procedure: marking the bet, remembering the player color, preventing new confusion, and settling correctly after the next spin.
Floor supervisors care about clarity. If a table has multiple imprisoned bets, multiple colors, and players still placing new action, control matters. The dolly marks the winning number, but the dealer also has to control special-status bets.
Surveillance wants the camera view to show exactly which bets were imprisoned and how they were resolved. A dispute after a zero is easier to solve when the table procedure is disciplined.
Common Mistakes
- Thinking En Prison pays a win after the next spin.
- Forgetting that recovery usually means getting the stake back, not earning profit.
- Assuming the rule applies to dozens, columns, or inside bets.
- Not asking what happens if zero appears again.
- Treating En Prison as identical in every casino.
- Continuing to bet too fast while an old bet is unresolved.
- Using a betting system without understanding the delayed settlement.
Hard Truth
En Prison gives the player a better zero rule, not control over the wheel. The bet may leave jail, but the game is still locked inside negative expectation.
FAQ
What is the house edge with En Prison?
Under common treatment for qualifying even-money bets, the effective edge is about 1.35%. Exact rules can vary by casino.
Does En Prison apply to all roulette bets?
Usually no. It normally applies only to even-money bets: red/black, odd/even, and high/low.
What happens when zero lands?
The qualifying even-money bet is held instead of being collected immediately. The next settlement depends on house rules.
If my imprisoned bet wins next spin, do I win profit?
Usually no. You normally get your original stake back without profit.
What happens if zero lands again?
That depends on the table rule. Some versions keep the bet imprisoned again; others may use a different settlement. Always check the posted rule.
Is En Prison better than normal European roulette?
Yes for qualifying even-money bets, because it reduces the cost of zero. It usually does not improve other bets.
Is En Prison better than La Partage?
Not necessarily. La Partage is simpler and immediate. En Prison can be similar in long-run edge but more complex in procedure.
Deeper Insight
En Prison is one of the rare roulette rules that changes expected value instead of just changing presentation.
Players often overvalue visible complexity. They think racetrack bets, wheel sectors, neighbor bets, and announced bets are smarter because they look more advanced. But unless the rule changes payouts, probabilities, or zero treatment, the edge usually stays the same.
En Prison matters because it changes the zero outcome.
The casino gives up some edge on even-money bets, but it may gain a more attractive table. Some players like the elegance. Some higher-bankroll players actively look for the rule. The lower edge can support longer play, and longer play can still be profitable if the table has enough action.
This is why edge alone is not the whole business story. Casinos also think about pace, average bet, staffing, occupancy, and player experience.
Formula / Calculation
For a normal single-zero even-money bet:
$$EV = \left(\frac{18}{37} \times 1\right) - \left(\frac{19}{37} \times 1\right) = -\frac{1}{37} = -2.70%$$
Under common En Prison treatment, the zero event creates an average half-stake loss over time:
$$EV \approx -\left(\frac{1}{37} \times 0.5\right)$$
$$EV \approx -\frac{1}{74} = -1.35135%$$
If a house treats repeat zero differently, the exact value can shift slightly.
Formula Explanation in Plain English
A normal single-zero even-money bet loses fully on zero. En Prison softens that result by giving the bet a chance to recover the stake. Under the common version, that makes the zero cost behave like an average half loss, which cuts the effective edge to about 1.35%.
Related Reading
Start with the main roulette guide and the core roulette odds page. For base game cost, read roulette house edge and French roulette house edge. Compare the zero rules with La Partage rule and En Prison rule. To price a session, use the house edge calculator or expected loss calculator. For the psychology of system play, read roulette hot numbers myth.