One extra pocket on a roulette wheel, a single green 00 sitting next to the 0, nearly doubles the house’s edge on every bet on the table. It’s a small physical detail with an outsized mathematical consequence, and most players never notice it happening.
37 Pockets vs. 38
A European wheel has pockets numbered 1 through 36 plus a single zero, 37 total. An American wheel adds a second zero, 00, for 38. Both zeros are green and belong to neither red nor black, neither odd nor even. They’re the house’s structural edge, the pockets that make every other bet on the table pay less than its true odds would suggest.
Running the Numbers
On a European wheel, a single-number bet has a 1-in-37 chance of hitting and pays 35:1, so the house edge works out to 2.7%. Add the second zero, and that same bet now has a 1-in-38 chance while still paying 35:1, pushing the house edge to 5.26%. The payout didn’t change; the odds of winning did.
Why American Wheels Still Exist
Mostly history and manufacturing inertia: American casinos adopted the double-zero wheel early, and it became the standard fixture on much of the US casino floor long before anyone was comparing house-edge percentages out loud. European casinos, largely developing later and under different regulatory traditions, standardized on the single-zero wheel instead.
The One Rule Worth Remembering
If a casino floor offers both wheel types side by side, the European wheel is the better bet on every single wager, with no exceptions. It’s one of the few places in a casino where the “better” choice is this unambiguous.
The Bet That Costs the Most on an American Wheel
The five-number bet, covering 0, 00, 1, 2 and 3, exists only on double-zero wheels. It pays 6 to 1 on five pockets out of 38, which gives it the worst edge on the whole layout at 7.89%. Every other bet on an American wheel carries the standard 5.26%, so simply avoiding that one line is worth more than any betting system.
What the Better European Rules Can Do
Some single-zero tables also apply la partage or en prison to even-money bets, which returns half of the stake when the ball lands on zero. That cuts the edge on red, black, odd, even, high and low bets from 2.7% to 1.35%, a figure that is worth looking for before you sit down or open a table online.
How to Tell Which Wheel You Are Looking At
Count the green pockets. Two zeros side by side, 0 and 00, mean an American wheel; a single 0 means a European one. The table layout gives it away too, since the American layout carries a 00 box beside the 0. Online, the game’s rules screen states the wheel type, and it is the first thing to check before you place a chip.
What the Edge Costs Over a Session
On a single-zero wheel every bet shares the same 2.7% edge, because each pays at odds worked out against 36 outcomes while 37 exist. On a double-zero wheel every bet shares 5.26%, apart from the five-number line. Stake 10 units on each of 200 spins, 2,000 units in all, and the expected loss is about 54 units on the European wheel against about 105 on the American one. Real sessions swing far either side of those averages, but the gap between the two wheels never closes.
Why No Betting System Fixes It
Progressions such as doubling after every loss do not change the edge. They only change how the same expected loss is spread: many small wins punctuated by a rare, large loss, with table limits capping how far the progression can run. Because every spin is independent, the extra zero costs exactly the same on the first spin of the night as on the last, whatever came up before it.
Questions About the Second Zero
Is the house edge really double on an American wheel?
Very nearly. A single-zero wheel carries a 2.7% edge on every bet, and a double-zero wheel carries 5.26% on every bet except the five-number line. The payouts are the same on both wheels; the extra pocket is the whole difference, because each bet is paid at odds worked out against 36 outcomes while 38 pockets exist.
Which bet should I avoid on an American wheel?
The five-number bet covering 0, 00, 1, 2 and 3. It pays 6 to 1 on five pockets out of 38, which puts its edge at 7.89%, the worst on the layout. Every other bet on that wheel carries the standard 5.26%, so leaving that one line alone is worth more than any betting pattern.
What do la partage and en prison change?
Some single-zero tables return half of an even-money stake when the ball lands on zero, through la partage, or hold it for the next spin, through en prison. That cuts the edge on red, black, odd, even, high and low from 2.7% to 1.35%. Check the rules screen of the table to see whether it is offered.
Can a betting system get around the extra zero?
No. Progressions such as doubling after every loss change how the expected loss is spread across a session, not its size, and table limits cap how far they can run. Every spin is independent, so the second zero costs the same on the first spin of the night as on the last.