Always Betting Red: What 1 Million Roulette Spins Actually Looks Like
Question
Is betting red on American roulette actually a 50/50 proposition?
Rules & assumptions
American roulette, 38 pockets: 18 red, 18 black, 0 and 00 both green. $5 flat bet on red, every single spin, no adjustments. Seed 43.
The experiment
1,000,000 independent spins simulated.
Results
| Metric | Value |
|---|---|
| Red | 472,837 (47.284%) |
| Black | 474,395 (47.440%) |
| Green (0 or 00) | 52,768 (5.277%) |
| Longest red streak | 18 spins |
| Longest non-red streak | 21 spins |
| Total wagered | $5,000,000 |
| Net result | -$271,630 |
| ROI | -5.433% |
Red landed 47.284% of the time, just under the true 18/38 ≈ 47.368% probability, well within normal sampling variance over a million spins. The gap between that number and an actual 50% is entirely explained by the 5.277% of spins that landed green — almost exactly the true 2/38 ≈ 5.263% — since every green spin is a loss for a red bet with nothing on the other side to balance it.
Short windows look very different from the long-run picture:
| Sample | Red | Black | Green | ROI |
|---|---|---|---|---|
| First 50 spins | 40.0% | 60.0% | 0.0% | -20.00% |
| First 500 spins | 48.4% | 47.2% | 4.4% | -3.20% |
| First 5,000 spins | 47.0% | 47.8% | 5.2% | -6.00% |
The first 50 spins in this run show zero greens at all and a red rate way off the true probability in either direction depending on the window; by 5,000 spins the numbers are already close to their long-run values. That's what convergence actually looks like: not a smooth march toward 47.37%, but a noisy one that only calms down once the sample is large.
Why it happens
A fair coin-flip bet needs exactly two equally likely outcomes. Roulette's red/black wager has three: red, black, and green. Every spin that lands on 0 or 00 is a loss for a red bettor, full stop, and those two green pockets are the entire reason red wins less than half the time instead of exactly half. Nothing about the wheel or the bet is rigged beyond that; the 5.26% edge is just what happens when a bet paying even money resolves against 20 losing numbers instead of 19.
Verdict
Red is not a 50/50 bet on an American wheel, because 0 and 00 aren't red or black. They're the entire house edge, sitting quietly outside the 50/50 framing the bet seems to promise. A European wheel with only one zero cuts that gap roughly in half; see American vs European Roulette for the side-by-side math.
Simulation and analysis by 0Stakes. Full methodology at /methodology/.