American Odds Explained: What +150 and −110 Mean
American odds look intimidating until you learn the one rule behind them: the number is always measured against $100. The sign — plus or minus — tells you which direction. Once that clicks, every line on the board is readable.
The minus sign: favorites (−)
A −110means you'd risk $110 to win $100. The bigger the number, the heavier the favorite: −250 risks $250 to win $100. Minus odds answer the question "how much do I bet to win a hundred?"
That standard −110you see on most point spreads and totals isn't random — the extra $10 is the vig(the book's built-in margin). It's why winning 50% of your bets still loses money over time.
The plus sign: underdogs (+)
A +150 means a $100 bet wins $150 in profit. The bigger the number, the bigger the underdog and the bigger the payout: +400 wins $400 on a $100 stake. Plus odds answer "how much do I win if I bet a hundred?"
Turning odds into a probability
Odds are just an implied probability in disguise. Quick conversions:
- Minus odds: odds ÷ (odds + 100). So −110 → 110 / 210 ≈ 52.4%.
- Plus odds: 100 ÷ (odds + 100). So +150 → 100 / 250 = 40%.
This is the most useful skill in sports research: once you can convert a line to a percentage, you can compare the book's number to your own estimate and spot when there's value.
The vig, in one sentence
Add up the implied probabilities on both sides of a bet and you'll get more than 100% — that overage is the sportsbook's cut. On a standard −110/−110 line it's about 4.5%. Beating the vig is the entire game.
Quick reference
- −110 → bet $110 to win $100 → ~52% implied
- +100 ("even money") → bet $100 to win $100 → 50%
- +150 → bet $100 to win $150 → 40% implied
- −200 → bet $200 to win $100 → ~67% implied
Next up: how these odds attach to different bet types in Moneyline, Spread & Total Explained, or jump straight to single-player numbers with What is a Player Prop?