Roulette Odds Calculator & Probability Guide
Calculate your exact win probability, expected return, and risk level. Before you play at UK online roulette sites, use this tool to compare the true mathematical odds of every bet on the table against the casino payout.
Last Updated: May 2026 • Verified by: Roulette UK Team
Interactive Bet Calculator
Select your wheel type (European is standard for UK) and input your bet to reveal the mathematical House Edge.
🎡 Roulette Odds & Payout Calculator
How to Use the Roulette Odds Calculator
An odds calculator doesn’t predict the future; it reveals the mathematical viability of your betting structure. Use the tool above to optimize your bankroll management before sitting down at a live table:
- Step 1: Select the Wheel Variant. Always toggle the calculator to “European” if you are playing in the UK. Switching it to “American” will immediately demonstrate how the extra double-zero (00) degrades your win probability across all bet types.
- Step 2: Input Your Base Unit. Enter your standard chip size (e.g., £5). The calculator will output your exact potential profit versus the statistical risk of losing that stake.
- Step 3: Analyze the Expected Value (EV). Use the tool to compare combining multiple inside bets (like 4 corners) versus a single outside bet (like a Dozen). You will quickly see that while coverage increases, the fundamental house edge remains static.
The Mathematics of Roulette: True Odds vs. Casino Payouts
To become a smarter player, you must understand the difference between “Odds of Winning” (Probability) and “Casino Payouts.” The gap between these two numbers is the House Edge—the fee you pay to play.
1. True Odds (The Real Math)
On a standard European Roulette wheel, there are 37 pockets (Numbers 1–36, plus a single Green 0).
- If you bet on a single number, you have 1 chance in 37 of winning.
- Mathematically, the “True Odds” against you are 36 to 1.
2. Casino Payouts (What You Get Paid)
If your number hits, the casino does not pay you 36 to 1. Instead, they pay you 35 to 1.
This discrepancy—paying 35 units when the true risk is 36 units—is how the casino guarantees a profit. On every spin, the Zero ensures that “Even Money” bets (Red/Black) are never 50/50. They are actually 48.65% to win.
Expected Value mathematically represents what you stand to win or lose per bet in the long run. If you bet £10 on Red on a European wheel, the math is:
(18/37 × £10) - (19/37 × £10) = -£0.27
This means for every £10 wagered, you mathematically forfeit 27 pence to the house.
The Probability of Betting Systems
Many players use roulette betting strategies like the Martingale or D’Alembert to try and beat the odds. While these systems manage your bankroll, they cannot change the game’s probability.
1. The “Martingale” Probability of Ruin
The Martingale involves doubling your bet after a loss. It relies on the idea that “Red has to hit eventually.” However, long losing streaks are statistically more common than players realize.
- Odds of 5 Reds in a Row: 1 in 32 (Approx 3%)
- Odds of 8 Reds in a Row: 1 in 263 (Approx 0.4%)
- Odds of 10 Reds in a Row: 1 in 1,376 (Approx 0.07%)
While 0.07% sounds rare, in a session of 1,000 spins (typical for an hour of speed roulette), there is a massive chance you will encounter a streak of 10. If you started with a £5 bet, your 10th bet would need to be £2,560. Because most tables have a £1,000 limit, the Martingale fails due to table caps.
2. The “Gambler’s Fallacy”
This is the false belief that past results influence future spins. “Black has hit 5 times, so Red is due!”
Understanding Variance vs. Volatility in Roulette
The calculator above provides your RTP (Return to Player). However, RTP only manifests over hundreds of thousands of spins. In a single 30-minute session, your results are governed entirely by Variance.
- Low Variance Play: Betting on Red/Black or Dozens. You win frequently, but the payouts are small. Your bankroll swings are gentle, allowing you to play for hours.
- High Variance Play: Betting on Straight-Up numbers. You will lose 36 out of 37 times on average. Your bankroll will steadily decline until a massive 35:1 spike restores it. If you lack the capital to survive the dry spells, high variance play will bust your account.
Complete Payout & Probability Charts
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Use this reference table to plan your betting strategy. Notice how “Coverage” correlates inversely with “Payout.”
European Roulette Odds (Single Zero | 2.70% Edge)
| Bet Name | Numbers Covered | Payout Ratio | Win Probability |
|---|---|---|---|
| Straight Up | 1 | 35 to 1 | 2.70% |
| Split | 2 | 17 to 1 | 5.40% |
| Street | 3 | 11 to 1 | 8.10% |
| Corner (Square) | 4 | 8 to 1 | 10.80% |
| Six Line | 6 | 5 to 1 | 16.20% |
| Dozen / Column | 12 | 2 to 1 | 32.40% |
| Even Money | 18 | 1 to 1 | 48.60% |
American Roulette Odds (Double Zero | 5.26% Edge)
Notice how the Win Probability drops across every single bet type, despite the payout remaining identical to the European wheel. This is why American roulette is highly detrimental to your bankroll.
| Bet Name | Numbers Covered | Payout Ratio | Win Probability |
|---|---|---|---|
| Straight Up | 1 | 35 to 1 | 2.63% |
| Basket Bet (Top Line) | 5 (0, 00, 1, 2, 3) | 6 to 1 | 13.16% (Worst Edge: 7.89%) |
| Even Money | 18 | 1 to 1 | 47.37% |
French “Called Bets” Odds
Once you master standard inside and outside bets, the next step in advanced roulette strategy is learning the French “Called Bets.” Located on the Racetrack betting layout, these wagers cover specific physical sections of the wheel rather than the numerical order on the felt. Here is the exact math and hit probability behind these premium bets.
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Voisins du Zero
Translates to “Neighbors of Zero.” This massive bet covers 17 numbers surrounding the green zero on the wheel. It requires 9 chips placed as splits, corners, and a trio. Because it covers nearly half the table, it yields a powerful 45.9% win probability.
Tiers du Cylindre
Translates to “Thirds of the Wheel.” This bet covers the 12 numbers positioned opposite the zero. It requires 6 chips placed purely as split bets. Covering almost exactly one-third of the wheel, it carries a solid 32.4% win probability.
Orphelins
Translates to “Orphans.” This covers the remaining two slices of the wheel not included in Voisins or Tiers (8 numbers total). It requires 5 chips (one straight-up and four splits) and offers a 21.6% win probability.
🛡️ Play Safely: Know Your Limits
Understanding the math and odds behind roulette is the first step in responsible play. Always remember that the house edge means the casino is mathematically guaranteed to win over the long term. Never gamble with money you cannot afford to lose. If you feel you are losing control, free and confidential support is available.
- GamCare & The National Gambling Helpline: Call 0808 8020 133 for free, 24/7 support.
- GambleAware: Access free tools and self-assessment quizzes at BeGambleAware.org.
- GAMSTOP: Register securely to universally self-exclude from all UK-licensed gambling sites.