If you’re a Roulette player, there are two very important numbers you should know. They’re the house edges for American Roulette (5.26%) and European Roulette (2.70%). There’s no skill involved in Roulette, so with average luck, you can expect to lose 5.26 units for every 100 units you bet playing the American version (not including the basket bet, which has a 7.89% house edge), and 2.70 units playing the European version.

We can calculate these house edges by looking at the odds that both wheels offer. The European wheel contains the numbers 1 through 36, plus the single zero (0), making 37 spaces in total for the ball to land. That extra space is where the house edge comes from. If you place a single bet of one unit on Black 20, you will win 35X your bet once every 37 spins (that’s 1-in-37 odds, or 36-to-1), and lose your bet the other 36 times. Here’s how the math looks:

(35 units)(1/37) – (1 unit)(36/37) = –1/37 unit = –0.0270 units

That final result still holds true when you make any other bet on the European wheel. Let’s say you wager one unit on Black instead of Black 20. You will be paid out at even money 18 times every 37 spins, and lose your bet the other 19 times:

(1 unit)(18/37) – (1 unit)(19/37) = –1/37 unit = –0.0270 units

Roulette Wheels Across America

With American Roulette and the double zero (00) added to the wheel, you’ll win 35X your single bet on Black 20 once every 38 spins, and lose your bet the other 37 spins, which works out like this:

(35 units)(1/38) – (1 unit)(37/38) = –2/38 unit = –0.0526 units

The math works for every bet you make on the American wheel – except for the basket bet (aka top line) that we mentioned earlier. The basket bet covers the numbers 0, 00, 1, 2 and 3, and it pays out at 6-to-1. That means you’ll win 6X your bet five times out of 38, and lose the other 33 spins:

(6 units)(5/38) – (1 unit)(33/38) = –3/38 unit = –0.0789 units

By understanding this relationship between the odds and the house edge, you can manage your Roulette bankroll more easily; there’s no need to change your bet size between the even-money outside bets (like Red/Black) and the long-shot inside bets (like the single bet). But you might want to bet smaller playing American Roulette compared to European Roulette, and smaller still when you make that basket bet. Your bankroll will thank you for it.