How La Partage and En Prison Rules Benefit Roulette Players

Roulette enjoys enduring popularity among casino players, largely thanks to its straightforward rules and a wide variety of betting options. Many unconventional variations of this casino staple have emerged over the years, but traditional single-zero versions like French and European Roulette remain players’ favorites.

This preference is no surprise, since players enjoy better odds and lower house edges at single-zero tables compared with double-zero games, where the casino holds twice as large an advantage.

But it gets even better, as some single-zero variations offer two unique rules, La Partage and En Prison, that cut the house advantage in half and further improve players’ chances with specific bets. Continue reading to learn more about these favorable rules and how they benefit roulette fans.

Bets Covered by La Partage and En Prison

Before we proceed any further, we would like to point out that the two rules in question apply only to certain outside bets. La Partage and En Prison cover even-money wagers that pay at odds of 1 to 1 and lose to the green zero, which gives the house its edge in roulette.

While dozens and columns also belong to the category of outside bets, they are beyond the scope of these favorable rules. Players can take advantage of them when betting on:

How the La Partage Rule Works

When available, La Partage takes effect when you bet on even-money selections and the ball lands in the zero pocket. Instead of losing your entire wager as you normally would, the dealer collects only half of the bet and returns the other half.

The La Partage rule essentially cuts your losses on even-money wagers to 50% when the zero appears. Here is an example that shows how this works.

How the En Prison Rule Works

Similar to La Partage, En Prison is another player-friendly rule that applies to even-money outside wagers like red/black, odd/even, and high/low. Under this rule, the player receives a second chance to win instead of losing half of the bet when the zero is spun. The dealer places a marker on the unsuccessful wager to indicate it is ‘in prison’.

The bet remains on the layout for a second spin and is released from its ‘imprisonment’ if it wins. The player effectively breaks even, as the dealer returns only the original wager without paying out any winnings. The rules regarding what happens when a second zero appears are largely casino-specific.

Impact on Players’ Expected Value

Roulette wheels contain green zero pockets for a reason, and it is not to give you extra betting opportunities. The addition of the zero allows the house to retain a fixed percentage of players’ total wagers in the long term. This percentage represents the house edge, that is, the mathematical advantage the casino holds over its patrons.

The house edge is always working against roulette players, regardless of what betting system they use. No strategy or betting pattern can help them overcome the negative expectation inherent in this game of chance.

Expected Value in Single-Zero Roulette

Impact of La Partage on Expected Value

Impact of En Prison on Expected Value

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Expected Value in Single-Zero Roulette

Determining the expected value (EV) for roulette players is fairly straightforward. Under European rules, roulette wheels contain a single zero, 18 black pockets, and 18 red pockets for a total of 37 numbers.

If you place a $1 wager on black, your probability of winning another dollar is 18/37 because there are 18 black pockets out of 37. The probability of losing your original dollar is slightly higher at 19/37. Given that, the expected value of your bet on black can be calculated as follows:

• EV = ($1) x (18/37) + (-$1) x (19/37)
• EV = 18/37 + (-19/37)
• EV = – 1/37
• EV = -0.027027

It becomes clear that the expected value of even-money wagers is -0.027027, corresponding to a house edge of 2.70%. In other words, you will lose approximately 2.7 cents out of every dollar you wager in the long run. The percentage is identical across all bet types in single-zero roulette, including inside wagers.

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Impact of La Partage on Expected Value

Both rules are advantageous to roulette players because they reduce the house edge, allowing you to lose less money in the long term. La Partage, in particular, halves the casino’s advantage because the player forfeits only half of their wager on even-money propositions when the zero appears. The expected value calculation is therefore slightly different.

EV = (1) x (18/37) – (1) x (18/37) – 1/2 x (1/37)

EV = -0.013513

As you can see, the expected value is still negative, but you will lose roughly 1.35 cents out of every dollar you bet on even-money propositions. It may not seem like much, but as the saying goes, a penny saved is a penny earned.

Gambling losses can accumulate over time when you play consistently, so why not lose less if you can? Accordingly, the house edge drops from the standard 2.70% to 1.35% when this rule is in place.

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Impact of En Prison on Expected Value

En Prison has a similar effect on players’ negative expected value, reducing it to -0.013513 under the standard rules of French Roulette. There is a minuscule increase in negative expectation for single, double, and triple-imprisoned wagers, as you can see in the table below.

It is fair to say the difference in house edge is extremely negligible across variations of the rule. Depending on the circumstances, some variants of the imprisonment rule are slightly less advantageous to roulette players than La Partage.

The bottom line is that you are better off playing games with either rule in place than versions where your even-money wagers lose outright when the dealer spins zero.

En Prison Rule Variation	Expected Value of Even-Money Bets
Standard French Rules	-0.013513 (1.35% house edge)
Single En Prison	-0.013878 (1.38% house edge)
Double En Prison	-0.013703 (1.37% house edge)
Triple En Prison	-0.013701 (1.37% house edge)

En Prison and La Partage are two mutually exclusive rules, which is to say they cannot both be in place simultaneously. We recommend you check beforehand which one applies in your chosen roulette variation. Our observations are that La Partage is more common in online variants of the game.

Online Roulette Games with La Partage and En Prison

La Partage and En Prison are not restricted to land-based casinos only. Players looking for a lower house edge can also find these advantageous rules in some online versions of the game. However, we should note that the availability of La Partage and En Prison is not immediately obvious.

Our suggestion is to navigate to the game’s rules or info section, where this information is usually found. Or you can spare yourself the hassle and choose one of the roulette variants we have handpicked for you. Some of them rely on random number generation for the outcomes, while others are hosted by human dealers in real time for a more authentic gaming experience.