The Single 0 Roulette Wheel: 37 Pockets, Its History and How It Differs From Double Zero

A single 0 roulette wheel has 37 pockets: the numbers 1 to 36 and one green zero. A double zero roulette wheel adds a second green pocket, marked 00, for 38 in total. That single extra pocket is the most important physical difference in roulette, because it nearly doubles the house edge, from 2.70% to 5.26%, according to the Wizard of Odds.

This guide focuses on the wheel itself: what's on it, where the single-zero design came from, how to tell the two wheels apart, and what the zero pockets do to every spin. For the full bet-by-bet comparison and session results, see our American roulette vs European comparison.

What's on a single zero roulette wheel

A roulette wheel is a spinning bowl with numbered pockets around its edge. On a single-zero wheel:

• 36 numbered pockets. The numbers 1 to 36, coloured 18 red and 18 black.
• One zero pocket. Marked 0 and coloured green. It is neither red nor black, odd nor even, high nor low.
• 37 pockets in total. Each one is equally likely on a fair spin, so every pocket has a 1 in 37 chance.

The betting layout next to the wheel repeats the numbers in a grid of 12 rows by 3 columns, with 0 at the top. That grid is where you place chips; the wheel is where the result is decided.

The double zero roulette wheel

A double 0 roulette wheel has everything the single-zero wheel has, plus a second green pocket marked 00:

• 36 numbered pockets, 18 red and 18 black, exactly as before.
• Two zero pockets, 0 and 00, both green.
• 38 pockets in total, each with a 1 in 38 chance.

The double zero wheel is often called the American wheel, and the single-zero wheel the European wheel. Our American roulette wheel guide covers the 38-pocket layout and its table in depth.

How to tell them apart

• On the wheel: count the green pockets. One means single zero; two means double zero.
• On the layout: look above the number 1, 2 and 3 row. A single-zero layout shows one 0; a double-zero layout shows 0 and 00 side by side.
• Online: check the game name and rules panel. "European" usually means single zero; "American" usually means double zero. If you aren't sure, look for a 00 on the betting grid.
• A third option exists. Some games use a triple-zero wheel with 39 pockets. Our triple zero roulette guide covers it.

A short history of the single-zero wheel

Roulette emerged in European casinos in the late 18th century, according to Britannica's summary of the game. Wikipedia's history of roulette notes that the game is often attributed in part to the French mathematician Blaise Pascal, and records an early form being played at the Palais Royal in Paris by 1796.

The single-zero wheel came later. Wikipedia credits the Blanc brothers with introducing it at Bad Homburg in 1843. Fewer zero pockets mean a lower house edge, and the single-zero game became closely linked with Monte Carlo.

Today both designs are in use, which is why roulette games are often labelled "European" or "American".

What one zero does to the odds

Every pocket on a fair wheel is equally likely, so the probability of any outcome is pockets covered divided by total pockets. Add a pocket and every number's chance drops a little, while payouts stay the same.

That's not a coincidence. A straight-up bet pays 35 to 1, so a winning 1 USDT bet returns 36 USDT, which would be a fair price on a wheel with only 36 pockets. Each zero pocket is a spin the house wins against outside bets, without paying fair odds on inside bets.

Here is how the extra pocket changes the win chance on a few common bets:

Every bet loses a little win chance on the double zero wheel, and none of the payouts rise to compensate. The full table for every bet type, including the five-number bet unique to double zero, is in our American vs European roulette comparison.

Bets that include the zero

On a single 0 roulette wheel, the zero is a number like any other for inside bets. You can bet on it straight up at 35 to 1, or include it in a split or street with neighbouring numbers on the layout. Those bets have the same 2.70% edge as every other standard bet, because the payout scale doesn't change. Betting on the zero doesn't "remove" the house's pocket; it simply makes zero one of the outcomes you win on, priced exactly like the rest.

On a double zero roulette wheel, 0 and 00 can each be bet straight up, and the American layout adds a five-number bet on 0, 00, 1, 2 and 3. That bet pays 6 to 1 and carries a 7.89% edge, higher than anything on a single-zero table.

Why the difference is easy to miss

On any one spin, the gap between the wheels looks tiny. Red wins 48.65% of the time with one zero and 47.37% with two, a difference of about 1.3 percentage points. In a 20-spin session you'd never notice it. The gap only becomes obvious over hundreds of spins, which is exactly where most of your total betting happens.

How often the ball lands on zero

Over 1,000 spins, you would expect the ball to land on a zero pocket about:

• 1,000 ÷ 37 = 27.0 times on a single 0 roulette wheel;
• 1,000 × 2 ÷ 38 = 52.6 times on a double zero wheel.

If you bet 1 USDT on red every spin, each zero costs you your stake. Those 27.0 and 52.6 zero hits match the average losses in our simulation below, which is the edge made visible.

What our simulation shows

We simulated 100,000 players on each wheel, each betting 1 USDT on red for 1,000 spins.

One extra pocket cut the share of players finishing ahead from 18.68% to 4.35%, and roughly doubled the median loss.

Single 0 roulette rules that lower the edge further

Some single-zero tables add a rule for even-money bets when the ball lands on zero. La partage returns half the stake; en prison holds the stake for the next spin. Both bring the edge on even-money bets down to about 1.35%, according to the Wizard of Odds and Britannica's article on roulette house odds. Our roulette house edge guide shows the arithmetic.

Strategy: choosing a wheel

• Pick single zero when you can. It's the only decision that halves the cost of every bet.
• Don't expect zero to be "due". A zero is 1 in 37 on every spin, whatever happened before.
• Remember the wheel doesn't change the swings much. Red on either wheel wins close to half the time; the difference shows up over hundreds of spins, not in one session.
• Check expected cost before you play. Our roulette payout calculator shows the win chance and expected loss for any bet on either wheel.

Single 0 roulette with USDT

If you play with a USDT bankroll, the wheel choice is your biggest cost lever, and network fees are the second. A 2 USDT withdrawal fee is the same as the expected loss on about 74 USDT wagered on a single-zero wheel (2 ÷ 0.027). Our USDT guides compare networks. For comparison, crypto-native games such as dice publish a 1% edge.

Common mistakes

• Assuming every online roulette game uses a single-zero wheel.
• Missing the 00 on the betting layout.
• Betting on zero to "cover" it: a zero bet has the same edge as any other number.
• Expecting the single-zero wheel to make short sessions profitable: it halves the cost, it doesn't remove it.

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