European vs American roulette: what the extra zero changes
A European wheel has 37 pockets (1 to 36 and one zero). An American wheel has 38 (a second zero, 00). Payouts are identical, so the extra pocket is a pure addition to the losing side: the house edge doubles from 1/37, about 2.70%, to 2/38 or 1/19, about 5.26%.
The two wheels side by side
Both wheels carry the numbers 1 to 36. The European wheel adds a single green 0, which makes 37 pockets. The American wheel adds a 0 and a 00, which makes 38. For the full derivation of the margin on every bet, see the guide to the roulette house edge; this guide isolates what the second zero does.
| Feature | European (single zero) | American (double zero) |
|---|---|---|
| Pockets | 37 | 38 |
| Green pockets | 1 (0) | 2 (0 and 00) |
| Straight-up payout | 35 to 1 | 35 to 1 |
| True odds against one number | 36 to 1 | 37 to 1 |
| Chance of one number | 1/37, about 2.70% | 1/38, about 2.63% |
| Chance of red (18 numbers) | 18/37, about 48.65% | 18/38, about 47.37% |
| Chance of a green pocket | 1/37, about 2.70% | 2/38, about 5.26% |
| House edge on a standard bet | 1/37, about 2.70% | 2/38 = 1/19, about 5.26% |
Why the payout does not change
Payouts are set as if the wheel had 36 pockets. A bet on one number pays 35 to 1, which would be fair on a 36-pocket wheel because a win returns 35 units plus the stake, 36 in all, against a 1 in 36 chance.
Adding pockets makes winning rarer without raising the payout. Whatever the wheel, the extra pockets are all losing ones for a standard bet, so the whole cost of the green pockets lands on the player.
The calculation, step by step
Stake one unit on a single number. On the European wheel, 1 pocket in 37 wins 35 units and the other 36 lose the unit.
(1/37 × 35) − (36/37 × 1) = (35 − 36)/37 = −1/37 ≈ −2.70%
On the American wheel, 1 pocket in 38 wins 35 units and 37 lose the unit.
(1/38 × 35) − (37/38 × 1) = (35 − 37)/38 = −2/38 = −1/19 ≈ −5.26%
The result is the expected value per unit staked: the average loss, which is the house edge. The ratio of the two edges is (1/19) ÷ (1/37) = 37/19, about 1.95, so the American wheel costs a little under twice as much per unit staked.
An even-money bet gives the same answer. Staking one unit on red wins on 18 pockets and loses on the rest. European: (18 − 19)/37 = −1/37. American: (18 − 20)/38 = −2/38. The edge depends on the number of green pockets, not on which bet is chosen.
What the difference costs over a session
The average cost is the edge multiplied by the total amount staked. The gap between the wheels therefore grows with every spin.
A player stakes KES 100 on each of 100 spins, KES 10,000 in total. On the European wheel the expected loss is 10,000 × 1/37 = KES 270.27, about KES 270. On the American wheel it is 10,000 × 1/19 = KES 526.32, about KES 526. The American wheel costs about KES 256 more on the same stakes.
These are averages over very many spins. Any single session can end above or below them, which is the point of the relationship between house edge and RTP: the return to the player is 1 minus the edge, here 36/37 (about 97.30%) against 36/38 = 18/19 (about 94.74%).
The one bet that is different
Most American wheels also offer a bet on five numbers: 0, 00, 1, 2 and 3. It pays 6 to 1. Five winning pockets out of 38 each return 7 units including the stake, so the return is (5 × 7)/38 = 35/38 of the stake, and the edge is 3/38, about 7.89%. This is higher than the 2/38 of every other standard bet on that wheel. There is no European counterpart because a single-zero wheel has no 00.
Does the wheel or the screen change the maths?
No. The pocket count and the payout table fix the edge, whether the ball runs on a physical wheel in a live dealer game or the result comes from a random number generator. Each spin is independent, so no earlier result changes the chance of the next one.
How a particular table is set up can vary, which is why the rules matter more than the name of the game. Some tables carry extra rules that return part of a stake when a zero lands; the effect depends on the precise rule, so read the displayed rules rather than assuming it.
What Kenyan rules say about displaying the wheel's odds
Regulation 20(2) of the Gambling Control (Conduct of Gambling Operations) Regulations, 2026 states that a licensee shall "display clearly rules of games, odds, house edge and average return to the player". Regulation 20(1) adds that casino games "must be authorized by the Authority".
In practice the number of zeros, the payouts and the stated edge should be readable before any stake. If the displayed edge is 1/37 or about 2.70%, the wheel is single zero; if it is about 5.26%, it is double zero. Gambling is addictive: play responsibly, and only if you are 18 or over.
Questions and answers
What is the difference between European and American roulette?
The wheel. A European (single-zero) wheel has the numbers 1 to 36 and one 0, so 37 pockets. An American (double-zero) wheel adds a 00, so 38 pockets. The payouts for each bet are the same on both.
Why does one extra pocket double the house edge?
Because the payouts stay calculated as if there were 36 pockets. Each green pocket is a pocket where every standard bet loses. Going from one green pocket to two doubles the losing share that the payouts do not cover, from 1/37 to 2/38 of the stake on average.
Is the chance of hitting a single number much lower on an American wheel?
Slightly lower: 1 in 38 (about 2.63%) instead of 1 in 37 (about 2.70%). The bigger change is in the payout, which stays at 35 to 1 although the true odds against are now 37 to 1.
Does the red or black bet change between the two wheels?
Its payout is 1 to 1 on both, but the chance of winning falls from 18/37 (about 48.65%) to 18/38 (about 47.37%), because two green pockets now lose it instead of one.
Can I tell which wheel a table uses?
Count the green pockets, or read the rules shown for the game. A licensed operator in Kenya must display the rules, odds and house edge of its casino games, so the number of zeros and the edge should be visible.