Roulette Probability Calculator
Calculate the exact probability of any roulette bet hitting on a single spin or over multiple spins. Understand streak probabilities and expected outcomes.
Formula:P(at least once in N spins) = 1 - (1 - p)^N
Per Spin Probability
2.70%
1 in 37.0
P(Win in 37 spins)
63.7%
Expected Appearances
1.00
in 37 spins
P(2 in a row)
0.073%
European has better odds
Type of bet to analyze
Calculate probability over this many spins
Probability Analysis for 1 Number
Single Spin
Win Probability:2.7027%
Odds:1 in 37.00
Fraction:1/37
Over 37 Spins
P(At Least 1 Win):63.71%
P(Zero Wins):36.29%
Expected Wins:1.00
Consecutive Win Probabilities
Probability of winning this bet multiple times in a row:
2 in a row
0.073%
3 in a row
0.0020%
5 in a row
0.000001%
10 in a row
0.0000000000%
Important: Independence of Spins
Each roulette spin is completely independent. If red has appeared 10 times in a row, the next spin still has the same probability of being red (~48.65% on European). The wheel has no memory. "Due numbers" and "hot numbers" are gambling fallacies.
Key Facts
- •Each spin is independent - past results don't affect future outcomes
- •European roulette has 37 pockets (0-36), American has 38 (0, 00)
- •Single number probability: 2.70% European, 2.63% American
- •Even-money bet probability: 48.65% European, 47.37% American
- •The "law of large numbers" doesn't mean short-term results will balance
Frequently Asked Questions
What is the probability of hitting a single number in roulette?
On a European wheel, the probability is 1/37 (2.70%). On an American wheel, it's 1/38 (2.63%). Over 37 spins on a European wheel, you have about a 63.4% chance of seeing your number at least once.
How does the number of spins affect probability?
More spins increase the chance of your bet appearing at least once. However, each spin remains independent - previous results don't affect future spins. This is why "due numbers" is a myth.
What is the probability of red appearing 5 times in a row?
On a European wheel, P(red) = 18/37 ≈ 48.65%. Five reds in a row has probability (18/37)^5 ≈ 2.73%. This is rare but happens regularly in casinos across thousands of spins.
Can I use probability to beat roulette?
No. Understanding probability helps set realistic expectations but can't overcome the house edge. Each spin is independent, and the house edge remains constant regardless of betting patterns or history.
Try These Examples
Quick-start with common scenarios
How this works
Calculations follow the published mathematics of the game — combinatorics for cards, probability theory for dice, and expected-value accounting for wagers. Results are verified against independent references (primarily Wizard of Odds). No calculation here is an opinion or recommendation; it is arithmetic applied to the rules of the game.
What this tool can’t do
When to consult a professional
This tool computes probability and expected value. It is not a betting system and cannot predict the outcome of any individual wager. If gambling is causing problems for you or someone you know, call the National Problem Gambling Helpline at 1-800-GAMBLER.
Sources
- [1]Wizard of Odds — Michael Shackleford, ASAIndustrywizardofodds.comAccessed Apr 21, 2026
Actuary; widely cited casino-game probability reference. Used for house-edge and EV verification.
- [2]National Council on Problem GamblingOfficial sourcencpgambling.orgAccessed Apr 21, 2026
Responsible-gambling guidance and 1-800-GAMBLER helpline.
Joseph OrdunaFounder & Software Engineer
Full-stack software engineer specializing in embedded systems, web architecture, and AI/ML. Founder of Practical Web Tools. Built the gesture-controlled drone IP acquired by KD Interactive (Aura Drone, sold on Amazon).
Per Spin Probability
2.70%
1 in 37.0
P(Win in 37 spins)
63.7%
Expected Appearances
1.00
in 37 spins
P(2 in a row)
0.073%