American roulette has 0 and 00 because the double-zero wheel preserves an extra green pocket while keeping the familiar standard payouts. That one additional losing outcome raises the casino’s mathematical advantage on ordinary bets from about 2.70% on a single-zero wheel to about 5.26% on a double-zero wheel.
The second zero is therefore not cosmetic. It changes the price of the game every time a player wagers on red, black, odd, even, a dozen, a column, or a number combination that does not include both green pockets.
The extra green pocket changes the denominator
A standard American double-zero wheel has 38 pockets:
- 18 red numbers;
- 18 black numbers;
- one green 0;
- one green 00.
A single-zero wheel has 37 pockets because 00 is absent.
The standard straight-up payout is 35 to 1 on either wheel. The payout does not improve merely because the double-zero wheel contains another possible result. That is where the extra house advantage comes from.
For a $1 straight-up wager on a single-zero wheel, one pocket wins and 36 lose:
Expected Value = (1/37 × $35) - (36/37 × $1)
= -$0.0270 approximatelyThe expected loss is about 2.70 cents for each dollar wagered, corresponding to a house edge of about 2.70%.
On a double-zero wheel, one pocket still wins, but 37 lose:
Expected Value = (1/38 × $35) - (37/38 × $1)
= -$0.0526 approximatelyThe expected loss is about 5.26 cents per dollar wagered, so the standard house edge is 5.26%.
The edge does not exactly double, but it gets close: 5.26% versus 2.70%.
Red and black are not fifty-fifty on a double-zero wheel
The layout visually encourages a simple thought: 18 red numbers and 18 black numbers must make red/black an even contest. The two green pockets break that symmetry.
A $1 bet on red has:
- 18 winning outcomes;
- 18 black losing outcomes;
- 0 as a losing outcome;
- 00 as a losing outcome.
So the wager wins 18 times in 38 possible outcomes and loses 20 times in 38:
EV = (18/38 × $1) - (20/38 × $1)
= -$0.0526 approximatelyThat is the same 5.26% edge as most standard inside bets on the same double-zero wheel. Red/black has lower volatility than a straight-up number because it wins more often, but it does not escape the mathematical cost created by 0 and 00.
This distinction is useful: hit frequency and house edge are not the same thing. A bet can win frequently and still have the same expected cost per dollar wagered as a much less frequent bet.
Why the double-zero form became associated with American roulette
The common story that “American casinos added 00 later” is too simple. Early roulette forms used both zero and double zero. During the nineteenth century, François and Louis Blanc became associated with promoting a single-zero wheel at Bad Homburg, making their version more attractive than competing double-zero games because it reduced the house advantage.
The single-zero format became strongly associated with European roulette, while the two-green-pocket form remained established in the United States and became known as American roulette. The Belgian National Lottery Museum’s roulette collection describes the older two-zero form and the later single-zero development.
For a modern player, the historical path matters less than the current arithmetic. The single-zero game gives the casino fewer green outcomes while standard payouts remain familiar; the double-zero game gives the casino one more.
Standard payouts do not expand when the wheel expands
A useful way to see the price difference is to compare the fair straight-up payout with the standard one.
| Wheel | Total pockets | Fair profit odds for one number | Standard profit payout | Standard house edge |
|---|---|---|---|---|
| Single zero | 37 | 36 to 1 | 35 to 1 | 2.70% |
| Double zero | 38 | 37 to 1 | 35 to 1 | 5.26% |
| Triple zero | 39 | 38 to 1 | 35 to 1 | 7.69% |
A fair double-zero straight-up bet would need to pay 37 to 1 in profit because 37 of the 38 outcomes lose. Standard roulette still pays 35 to 1. The missing value is the casino advantage.
Triple-zero roulette extends the same mechanism. Add another green pocket without raising the standard payout and the ordinary house edge rises again, to about 7.69%. That is why identifying the actual wheel is more important than assuming every roulette table is mathematically interchangeable.
The Nevada Gaming Control Board’s published double-zero roulette rules provide a modern example of a 38-pocket format.
Double zero is not more likely than any other individual pocket
00 looks unusual because it is written differently, appears in green, and occupies a prominent place on the betting layout. None of that makes it more likely than 17, 26, or any other individual pocket on a properly balanced wheel.
On a 38-pocket wheel:
P(00) = 1/38
P(17) = 1/38
P(any named single pocket) = 1/38The same principle applies to 0. The casino advantage does not come from either green pocket being secretly “stronger.” It comes from the fact that most standard wagers lose when either green result appears while their payout remains unchanged.
The cloth layout can also create false intuition. Numbers adjacent on the betting layout are not necessarily adjacent on the physical wheel. A cluster that looks meaningful on the felt may be scattered around the wheel order.
The five-number basket is an important American-wheel exception
Most conventional wagers on a double-zero wheel carry the familiar 5.26% house edge, but the five-number bet covering 0, 00, 1, 2, and 3 is worse under the traditional 6-to-1 payout.
Its probability of winning is 5/38. With a 6-to-1 profit payout, the expected value is:
EV = (5/38 × $6) - (33/38 × $1)
= -$3/38
≈ -7.89%So “all roulette bets have the same edge” is only approximately true for the standard bet families. The American five-number basket is a notable exception. Paytables and special variants can create others.
La partage and en prison can make a single-zero table even cheaper
Some single-zero games offer special treatment when zero appears on an even-money wager.
Under la partage, the player may lose only half the stake when the ball lands on zero. Under en prison, the wager may be held for another spin under the specific table rule. These provisions can reduce the effective house edge on qualifying even-money bets, often to about 1.35% under the standard la-partage treatment.
They do not automatically apply to every single-zero wheel, and they generally do not improve all inside bets. Read La Partage and En Prison for the rule details.
The lesson is that number of zeros is the first filter, not the last one. A careful comparison also checks special rules and any altered payouts.
A lower table minimum does not necessarily mean a cheaper roulette game
Players often compare tables by minimum bet because that is the most visible number. But expected cost depends on total action and house edge.
Suppose a player puts $10 per spin through a double-zero wheel for 100 spins:
Total Action = $10 × 100 = $1,000
Expected Loss ≈ $1,000 × 5.26% = $52.60At $15 per spin for 100 spins on a single-zero wheel:
Total Action = $15 × 100 = $1,500
Expected Loss ≈ $1,500 × 2.70% = $40.50The higher-minimum table produces the lower theoretical cost in that example because the house edge is much lower. Real sessions vary, and a player may make a different number of spins, but the comparison shows why minimum bet alone is not enough.
Use the Roulette Bet Comparison Tool to compare the wheel, bet type, probability, payout, and house edge together.
Changing bet style cannot remove the second zero
A player may switch from single numbers to red/black because the latter feels safer. The variance changes dramatically: an even-money bet wins much more often and produces smaller swings. The underlying standard double-zero edge, however, remains 5.26%.
Likewise, betting more numbers does not cancel 0 and 00. It simply changes how much of the wheel is covered and how the payoff behaves when one of those covered numbers wins.
No staking progression changes the number of pockets or the payout schedule. Increasing the wager after losses changes exposure, not probability.
What to check before choosing a roulette table
A useful comparison takes less than a minute:
- Count the green pockets. Single zero is generally cheaper than double zero under standard payouts; double zero is generally cheaper than triple zero.
- Check the actual payout table. Electronic, multiplier, and promotional variants may alter conventional returns.
- Look for la partage or en prison. These can improve qualifying even-money bets on some single-zero games.
- Notice special wagers. The American five-number basket has a higher edge than the usual 5.26% double-zero bets.
- Estimate total action. Bet size multiplied by spins matters more than the minimum sign by itself.
For the physical and rule differences, continue with Roulette Wheel Differences and the main Roulette guide.
The second zero is a pricing decision built into the wheel
American roulette does not need 00 for the game to function. The ball could still land, numbers could still be paid, and red/black could still be offered with only one green pocket. The second zero exists because the double-zero format is a historically established version of roulette that gives the house another favorable outcome without increasing conventional payouts.
That is the entire mechanism. More possible losing outcomes, same standard payout, higher expected cost. Once that is understood, the practical choice between single-, double-, and triple-zero roulette becomes much easier to evaluate.