An Odd/Even bet is a roulette outside wager on the parity of the winning number. You choose Odd or Even before the spin. A winning wager normally pays 1 to 1, but the green zero pocket—and double zero on an American wheel—belongs to neither side of the bet.
That last point is the entire price of the wager. Odd and Even each cover 18 numbered pockets from 1 through 36. A single-zero wheel has 37 pockets, so the bet is not a 50/50 proposition. A double-zero wheel has 38 pockets, making the gap larger.
What the Odd and Even boxes actually cover
The roulette layout divides the ordinary numbers into two parity groups:
- Odd: 1, 3, 5, 7, 9, and so on through 35.
- Even: 2, 4, 6, 8, 10, and so on through 36.
Zero is printed as 0, but it is not included in the Even box. On a double-zero wheel, 00 is also excluded. This is a casino-bet definition, not a lesson about whether zero has mathematical properties associated with even numbers in number theory.
The practical settlement rule is simpler: the Odd box wins only when one of the 18 odd numbers lands; the Even box wins only when one of the 18 even numbers lands. Green pockets lose unless a special table rule says otherwise.
| Result | Bet on Odd | Bet on Even |
|---|---|---|
| 17 | Win | Lose |
| 22 | Lose | Win |
| 0 | Lose under standard rules | Lose under standard rules |
| 00 | Lose under standard double-zero rules | Lose under standard double-zero rules |
Even money does not mean even probability
The phrase even money describes the payout, not the chance of winning. If you stake $20 and win, a 1-to-1 payout gives $20 in profit and returns the $20 stake. If you lose, the $20 stake is gone.
On a single-zero wheel:
- winning pockets = 18;
- losing pockets = 19;
- probability of winning =
18 / 37 ≈ 48.6486%; - probability of losing =
19 / 37 ≈ 51.3514%.
On a double-zero wheel:
- winning pockets = 18;
- losing pockets = 20;
- probability of winning =
18 / 38 ≈ 47.3684%; - probability of losing =
20 / 38 ≈ 52.6316%.
The payout stays 1:1 while the losing side contains the extra green pocket or pockets. That mismatch creates the house edge.
House edge on single-zero and double-zero Odd/Even
For a $1 stake on single-zero roulette, the expected value is:
EV = (18/37 × $1) - (19/37 × $1) = -$0.027027...
The house edge is therefore about 2.70%.
For a $1 stake on standard double-zero roulette:
EV = (18/38 × $1) - (20/38 × $1) = -$0.052632...
The house edge is about 5.26%.
That does not mean the casino removes 2.70% or 5.26% from every individual bet. A single wager either wins or loses. House edge is a long-run expectation across repeated comparable action.
If a player makes 100 wagers of $10 on Odd at a standard single-zero table, total action is $1,000. The mathematical expected loss is approximately:
$1,000 × 0.027027 ≈ $27.03
The actual session could finish far ahead or far behind. The $27.03 figure describes the average built into the wager over repeated trials, not a session forecast.
Odd/Even versus Red/Black and High/Low
Odd/Even belongs to the same family of outside even-money wagers as Red/Black and High/Low. On the same standard wheel and under the same zero rule, these bets normally have the same house edge because each covers 18 of the ordinary 36 numbers.
What changes is the grouping:
- Odd/Even groups by parity.
- Red/Black groups by wheel color.
- High/Low groups 1–18 against 19–36.
None of those groupings includes zero. Choosing one family instead of another does not remove the green-pocket disadvantage.
Why zero causes so much confusion
Players sometimes say, “Zero is an even number, so Even should win.” That mixes ordinary mathematical classification with the contract printed on a roulette layout.
Casino wagers are resolved by their posted coverage. A straight-up bet on zero can win when 0 lands. An Even wager does not cover 0 unless an explicitly stated special rule changes the settlement. The same principle applies to many casino terms: the label is shorthand for a defined set of outcomes, not every everyday interpretation of the word.
The Zero and Double Zero glossary pages explain why the green pockets matter across roulette wagers.
La Partage and En Prison can change the zero result
Some roulette tables use a special rule for even-money bets when zero lands. Two well-known examples are La Partage and En Prison.
Under a common La Partage treatment, an even-money wager loses only half its stake when a single zero appears. That changes the expected value materially. Under an En Prison treatment, the wager may remain unresolved or be carried forward according to the table’s stated procedure.
These rules are not automatic features of every single-zero game. A player should verify the table sign or rules before assuming that Odd/Even receives special protection on zero. See La Partage for the terminology.
A streak of Odd or Even does not change the next spin
Suppose the last eight spins were:
Odd, Odd, Even, Odd, Odd, Odd, Even, Odd
That history can be counted and described, but on a fair wheel it does not alter the pocket distribution for the next spin. An Even result is not “due” because Odd appeared repeatedly, and Odd is not more likely because it appears “hot.”
The wheel has no memory of the scoreboard. If the physical probabilities have not changed, the next spin still begins with the same 18 winning pockets for the selected parity group and the same green-pocket disadvantage.
For the broader reasoning error, see Gambler’s Fallacy and Why Hot and Cold Roulette Numbers Do Not Predict the Next Spin.
Betting systems do not repair the parity math
A progression can change how much is staked after wins or losses, but it does not change which pockets belong to Odd or Even. Martingale, reverse Martingale, cancellation systems, and “switch after three” rules are money-management patterns layered on top of the same underlying wager.
If the next $10 Even bet has a 2.70% house edge on a single-zero wheel, making the next stake $20 after a loss does not make that $20 bet positive expectation. It simply puts more money at risk on the next independent decision.
This is why Even Money Bet and Outside Bet should be read as probability-and-payout terms, not strategy labels.
This standard treatment is also reflected in Nevada’s published single-zero Live Roulette rules, which list Even and Odd among the 1-to-1 wagers on a 37-pocket wheel. The posted rules of the table always control, especially where a property uses a special zero rule. See the Nevada Live Roulette Rules of Play.
Table limits matter when a progression grows
Odd/Even is often used in betting systems because the payout is 1:1 and the settlement is easy to follow. But a progression can reach the table maximum quickly.
Starting at $10 and doubling after each loss produces this sequence:
$10 → $20 → $40 → $80 → $160 → $320 → $640
After six consecutive losses, the next stake would already be $640. The accumulated amount risked is much larger than the original $10, and a finite bankroll can stop the sequence before a recovery bet occurs. Table Limit explains the operational ceiling.
How the casino sees the wager
From the table’s operational side, Odd and Even are routine outside bets. The dealer needs to identify the winning number, clear losing positions, and pay the winning parity box at the posted rate. There is no special “streak” procedure and no separate mathematical treatment based on recent history.
For player rating, repeated Odd/Even wagers contribute to the same broad idea of action as other roulette wagers. The important inputs are money wagered, time, game conditions, and the property’s rating method—not whether a player believes the current run is hot or cold.
The definition to remember
An Odd/Even bet is a 1-to-1 outside roulette wager covering 18 numbers. On standard roulette, zero and double zero are not included in either parity group. That is why the bet can look nearly balanced while still carrying the wheel’s normal house edge.
Use Roulette for the full game, Outside Bet for the wager family, and Zero for the green-pocket effect.