What are outside bets in roulette?
Outside bets in roulette cover large sections of the number grid and are placed in the labelled zones around the edge of the betting layout. They win more often than inside bets but pay at lower odds.
Types of outside bets
Red or black pays 1:1 and covers 18 numbers. Odd or even also pays 1:1. High (19-36) or low (1-18) pays 1:1. A dozen bet covers either 1-12, 13-24, or 25-36 and pays 2:1. A column bet covers all 12 numbers in one of the three vertical columns on the layout and also pays 2:1.
What outside bets don’t cover
Zero (and double zero in American roulette) falls outside all outside bet categories. That’s the house’s margin. On a 1:1 bet covering red, you’re not actually covering 50% of outcomes — you’re covering 18 out of 37 (or 38) numbers. Zero is neither red nor black, odd nor even, high nor low. That gap between 50% and the actual probability is where the house edge lives.