Understand roulette. Not just where to place the chips.
The rules, bets, mathematics, strategies, wheel physics and probability of casino roulette, explained with interactive tools and simulations.
37 pockets in wheel order, 0 first · red 18 · black 18 · green 1
No bet selected
pockets37 (0–36)
house edge2.70% on every bet
zerosingle, green
hinthover a pocket · tap the table
01 · Roulette in 5 minutes
One round, start to finish
01
Place chips
Inside the number grid or on the outside boxes. Several bets at once are normal.
02
Ball is launched
The dealer spins the rotor one way and sends the ball the other way along the track.
03
No more bets
The dealer waves a hand over the layout. Chips can no longer be moved.
04
Ball drops
It falls through the deflectors into one of 37 pockets. The dealer marks it with the dolly.
05
Settlement
Losing chips are cleared first, then winners are paid at the bet’s fixed odds.
02 · Understand the table
The grid is the wheel, unrolled
Tap numbers to place straight-up chips, or an outside box to cover a group. The wheel above highlights the same pockets, so you can see that table neighbors are not wheel neighbors.
Bet builder · stake $10 per number
pockets37 (0–36)
house edge2.70% on every bet
zerosingle, green
hinthover a pocket · tap the table
03 · Main bet types
Fewer numbers, bigger payout, same edge
04 · Probability & house edge
Why every bet loses 2.70%
Short answer
European roulette has a house edge of 2.70% on every standard bet.
Why
The casino pays a straight-up win at 35:1 even though there are 37 possible outcomes. Fair odds would be 36:1. The missing unit, spread over 37 outcomes, is the edge.
Formula
EV = (1/37)·(+35) + (36/37)·(−1)
= 35/37 − 36/37
= −1/37 ≈ −0.0270Same bet, three wheels
European
37 pockets · 1 zero
2.70%
American
38 pockets · 0 and 00
5.26%
French
37 pockets · la partage
1.35%
French rules halve the edge on even-money bets only: when zero hits, la partage returns half the stake and en prison holds it for another spin. Everything on this site assumes the European wheel unless stated.
05 · Strategy
What betting systems actually do
A system changes the shape of your results, not their average. Martingale doubles after each loss, so it wins small amounts often and loses a large amount rarely. The expected loss per dollar wagered stays at 2.70%.
loss #next bettotal riskedp(reach)
0$10$10100.00%
1$20$3051.35%
2$40$7026.37%
3$80$15013.54%
4$160$3106.95%
5$320$6303.57%
6$640$1,2701.83%
7$1,280$2,5500.94%
Base bet $10, table limit $500. After six losses the next bet is $640, above the limit: the progression breaks with $630 lost. The chance of six straight losses on red is (19/37)^6 = 1.83%, roughly once every 55 attempts.
Martingale vs flat bet · one seeded session150 spins · red · end: mart +$680 · flat $-120
06 · Roulette Lab
Hot numbers are usually just noise
A fair wheel produces lopsided samples all the time. The Lab covers wheel and ball physics, bias detection, sample size and the statistics needed to tell a real defect from a lucky streak.
spins370
hottest pocket20 · 16 hits (expected 10)
chi-square (df 36)32.8
p-value0.62
verdictno evidence of bias
Observed hits per pocket · wheel orderexpected 10 each
09
3213
158
1914
46
215
214
2515
178
345
65
2710
1310
3610
117
3010
89
237
106
512
249
1612
3310
110
2016
1413
3111
914
228
1812
2913
77
2813
1212
357
38
2612
Seeded fair-wheel sample. The darkest cell looks like a “hot number”; the chi-square test says the whole pattern is ordinary.
07 · Interactive tools
Run the numbers yourself
roulette-odds-calculator/Roulette Odds CalculatorProbability and payout for any betroulette-payout-calculator/Roulette Payout CalculatorReturn and net profit for a stakebet-builder/Bet BuilderCover numbers, see edge and expected losswheel-visualizer/Wheel VisualizerSectors, neighbors and call bets on the wheelroulette-session-simulator/Roulette Session SimulatorOne session, spin by spinroulette-strategy-simulator/Roulette Strategy Simulator10,000 sessions of any systemroulette-martingale-simulator/Roulette Martingale SimulatorHow often the progression breaksroulette-bankroll-calculator/Roulette Bankroll CalculatorHow long a budget lasts at a given pacerisk-of-ruin-calculator/Risk of Ruin CalculatorChance of busting before a targetroulette-wheel-bias-analyzer/Roulette Wheel Bias AnalyzerChi-square test on your own spin log
08 · Live roulette
A real wheel, a camera, and a betting window
A live table streams a physical wheel from a studio. The result is read by a dealer and by camera-based recognition, then pushed to every player's screen. The odds are the European odds; what changes is pace, latency and the betting window.
How live roulette works →00:00physical
Studio wheel
A physical wheel, usually 80 cm, spun by a dealer
00:00~1–3 s
Cameras and encoding
Several angles, encoded and pushed to a CDN
00:2015–30 s
Betting window
Opens after the previous payout, closes at “no more bets”
00:45< 1 s
Result recognition
Dealer confirms; optical recognition reads the pocket
00:50automatic
Settlement
Server settles bets, stream shows the dolly
09 · History & culture
From Pascal's workshop to Monte Carlo
1655Pascal’s wheelBlaise Pascal experiments with a perpetual-motion machine; the spinning wheel outlives the idea.
1796ParisA novel describes roulette with both 0 and 00 in a Palais-Royal gaming house.
1843Bad HomburgFrançois and Louis Blanc introduce the single-zero wheel to undercut rival casinos.
1863Monte CarloBlanc takes over the casino at Monaco; the single zero becomes the European standard.
c. 1880Jagger’s wheelJoseph Jagger watches the wheels for weeks and exploits a biased one at Monte Carlo.
1891Charles WellsWells “breaks the bank” repeatedly; the feat becomes a music-hall song.
10 · Explore the knowledge base