Roulette Odds and Probability: Payouts, House Edge and RTP
Roulette probability depends on the number of pockets and the settlement rules. The examples below assume a fair wheel with equally likely pockets and independent spins. A payout ratio, winning probability and theoretical return are different quantities.
Probability Is Not the Same as Odds Against
A conventional European wheel has 37 pockets: 1–36 and zero. A single chosen number therefore has a 1/37 probability, approximately 2.70%. The odds against it are 36:1, because there are 36 losing pockets for one winning pocket. The conventional profit payout is 35:1.
For a one-unit straight-up stake, a win returns 36 units including the stake. Expected return is 36/37, approximately 97.30%, leaving a house edge of 1/37, approximately 2.70%. “One in 37” must not be described as “37 to 1” odds against.
Single-Zero and Double-Zero Wheels
A conventional American wheel adds 00, producing 38 pockets. A single-number probability becomes 1/38, approximately 2.63%. With the same 35:1 profit payout, expected return is 36/38, approximately 94.74%, and house edge is 2/38, approximately 5.26%.
The single-zero return is therefore 97.30% versus 94.74%, not nearly twice as large. It is the expected loss percentage that is roughly halved. Most conventional double-zero wagers share the 5.26% edge; the five-number basket paying 6:1 has an edge of approximately 7.89%.
Conventional Single-Zero Bet Probabilities
Payouts in this table are profit ratios. The original winning stake is returned separately. Percentages are rounded.
| Bet Type | Numbers Covered | Payout | Probability (Win %) |
| Straight Up | 1 | 35:1 | 2.7% |
| Split | 2 | 17:1 | 5.4% |
| Street | 3 | 11:1 | 8.1% |
| Corner | 4 | 8:1 | 10.8% |
| Six Line | 6 | 5:1 | 16.2% |
| Column/Dozen | 12 | 2:1 | 32.4% |
| Red/Black | 18 | 1:1 | 48.6% |
| Even/Odd | 18 | 1:1 | 48.6% |
| High/Low | 18 | 1:1 | 48.6% |
Zero Concessions Change Settlement
A qualifying La Partage rule returns half an even-money stake on zero. This changes the expected loss to half of 1/37, approximately 1.35%. En Prison holds the qualifying stake subject to a later result; treatment of repeated zeros matters. See the French roulette explanation rather than assuming every version has identical rules.
Multiple Spins and Conditional Probability
On a fair single-zero wheel, red occupies 18/37 pockets. The probability that two specified consecutive spins are red is (18/37)², approximately 23.67%; for five it is (18/37)⁵, approximately 2.73%. Once four reds have already occurred, the next independent spin is still red with probability 18/37, approximately 48.65%.
A probability for one specified sequence is different from the probability of seeing that sequence somewhere in a longer session. The latter depends on session length and overlapping possibilities.
RTP Does Not Promise a Refund
A theoretical return of 97.30% is an expectation over stakes under the stated model. It does not mean a person who starts with $100 will finish with $97.30. Turnover, repeated stakes and random variation affect actual results.
Bets with more frequent small payouts can have the same house edge as less frequent larger payouts. Different variance does not imply a protected balance or a guaranteed session length.
Related Explanations
See inside and outside bets, American roulette and its basket exception, and roulette system claims. These calculations explain rules and do not establish availability of a particular version in Canada.
Related reading: How Slot Probabilities Work: Reels, Weights and Returns · Baccarat Odds and House Edge: Payout Assumptions Explained.
