European roulette (single-zero) has a 2.70% house edge across standard bets; American roulette (double-zero) has 5.26%. That edge is the same on red/black and on a single number—but volatility is not. Standard deviation per $1 bet is about 1 unit on even-money and roughly 5.76 units on a straight-up number (American wheel), which means much wilder swing potential for the same expectation.
House edge basics: European vs American vs French rules
On a 37-number European wheel, the house edge is 1/37 ≈ 2.70% on all standard bets. Add 00 to make an American 38-number wheel and the edge rises to 5.26%. These figures are consistent across authoritative roulette references and are a first filter when choosing a table.
French-rule tables can soften even-money bets further. With La Partage or En Prison, an even-money stake that hits 0 is only half-lost or held, cutting the edge on even-money bets to about 1.35% on a single-zero wheel. If you see these rules offered, they’re materially more favorable for even-money betting.
What volatility means in roulette
Volatility describes how widely results swing around the average. For one spin on an American wheel, the standard deviation (per unit bet) is about 0.999 for an even-money wager and about 5.763 for a straight-up single number—same negative expectation, radically different spread. Over n spins, standard deviation scales by √n, so session swing potential grows with length, especially for high-variance bets.
A striking implication: although both bets lose the same in expectation, the probability of being ahead after a finite session differs. Published calculations show that after 100 even-money spins, the chance of being up is roughly 26.5%, whereas for 100 single-number spins it’s about 49.2%—a volatility effect, not an edge. The downside tails are nastier for the single-number approach.
Red/black math vs straight-up number
Even-money (red/black)
European probability of a win on red is 18/37 ≈ 48.65% with a 1:1 payout; American is 18/38 ≈ 47.37%. Expectation per $1 is −1/37 on European and −1/19 on American (same as 2.70% vs 5.26% house edge). Variance is low compared to inside bets, which makes bankroll swings smaller per spin.
Single number (straight-up)
European win probability is 1/37, with a 35:1 payout; American is 1/38 with 35:1. The expected loss rate matches the wheel’s house edge, but variance is high because wins are rare and large. On American wheels, per-spin standard deviation is ~5.76 units for a $1 stake, illustrating how session results can be very far from the mean in both directions.
How rule sets change even-money bets specifically
If you enjoy red/black or other even-money wagers, French rules are your friend. La Partage/En Prison effectively halves the edge on those bets to about 1.35% on a single-zero wheel by mitigating what happens on 0. This does not give you an advantage, but it slows expected loss and smooths results.
Putting it together: choosing a volatility profile
If you prefer steadier sessions and longer time-on-bankroll, favor even-money bets on a single-zero table, ideally with La Partage or En Prison. If you enjoy long dry spells punctuated by big pops, straight-up numbers provide that high-variance profile—but set smaller unit sizes and tighter stop-losses. The house edge doesn’t change with the bet type on a given wheel; the risk experience does.
Practical checklist for table selection and staking
- Prefer European (single-zero) over American (double-zero); you cut the edge from 5.26% to 2.70%.
- For even-money play, hunt for La Partage/En Prison; you halve the edge on those bets to about 1.35%.
- Match stake to volatility: smaller units for single-number betting; you’re managing standard deviation, not changing expectation.
- Know your true hit chances: red/black is 18/37 (EU) or 18/38 (US); straight-up is 1/37 or 1/38.
- Remember payment method doesn’t alter wheel math; choose rules and volatility profile first.
Responsible gambling resources
If gambling stops being fun, take a break and use formal tools. In Great Britain, the Gambling Commission explains self-exclusion options, and GAMSTOP lets you exclude from all GB-licensed online operators with one request.
Sources and further reading
• Wizard of Odds: European roulette basics and 2.70% edge; American vs European overview.
• Wizard of Odds (Ask the Wizard): per-spin standard deviations and “probability of being ahead” comparisons by bet type and session length.
• Wizard of Odds: House edge table across popular games, including roulette single-zero and double-zero.
• Omni Calculator (Roulette): red/black covers 18/37 (EU) and 18/38 (US); 1:1 payout.
• Wizard of Vegas: French rules cutting even-money house edge to about 1.35%.
• UK Gambling Commission: self-exclusion information; GAMSTOP official site.
