Count pockets before trusting a payout.
Roulette is one of the cleanest casino games to audit mathematically.
Rule tools
What these roulette tools work out
The bet EV calculator takes a wheel, the number of pockets that win and the payout, and returns the win probability, the fair payout and the house edge. The rule comparison takes a stake and a number of spins and shows the expected cost on a single-zero wheel, a double-zero wheel and a single-zero wheel with La Partage.
A worked example
Bet $10 on red on a single-zero wheel. Eighteen of the 37 pockets win and pay 1 to 1, and 19 lose, so you expect to lose 1/37 of each bet: 2.70%, or 27 cents per $10. On a double-zero wheel two of 38 pockets are zeros, and the edge almost doubles to 5.26%. Fifty spins at $25 is $1,250 of action: about $16.89 expected with La Partage, $33.78 on single zero and $65.79 on double zero.
What they assume
Every pocket is equally likely, payouts are the standard ones, and each figure is a long-run average, not a forecast for one session. See wheel types and house edge, La Partage and En Prison and roulette myths.