Betting odds are prices. They tell you how much you risk, how much you win, and what the market thinks about the probability of each outcome. Every number on a sportsbook — from a game spread to a player prop — follows the same math. Learn it once and you'll never look at a line the same way.
American Odds in 60 Seconds
Negative odds (-110, -150, -200) = the favorite. The number is how much you risk to win $100. At -150, you put up $150 to win $100.
Positive odds (+110, +150, +200) = the underdog. The number is how much you win on a $100 bet. At +200, your $100 returns $200 profit.
The standard line is -110/-110. That gap between -110 and even money (+100) is the vig — the sportsbook's cut. You risk $110 to win $100, which means you need to win 52.4% of the time just to break even.
| Odds | You Risk / Win | Implied Probability |
|---|---|---|
| -200 | Risk $200 to win $100 | 66.7% |
| -150 | Risk $150 to win $100 | 60.0% |
| -110 | Risk $110 to win $100 | 52.4% |
| +100 | Risk $100 to win $100 | 50.0% |
| +150 | Win $150 on $100 bet | 40.0% |
| +200 | Win $200 on $100 bet | 33.3% |
The Three Bet Types
Moneyline — Pick the winner, no spread. Lakers -180 vs. Celtics +155 means you risk $180 to win $100 on LA, or risk $100 to win $155 on Boston.
Point Spread — The underdog gets a head start. Bills -6.5 means Buffalo must win by 7+ for your bet to cash. Dolphins +6.5 means Miami can lose by up to 6 and you still win. Usually priced at -110 on both sides.
Totals (Over/Under) — A bet on the combined score. NBA game total of 224.5 means you're betting whether both teams combine for more or fewer than 225 points.
Totals connect directly to props. A game total of 235 signals a fast-paced, high-scoring environment — which inflates individual player lines. A total of 205 means a defensive grind that suppresses counting stats. A player's 24.5 points line means something different in each game.
Implied Probability: Where the Edge Lives
Every set of odds implies a probability. Convert odds to implied probability, compare it to your own estimate, and you'll know if there's value.
For negative odds: Implied probability = |Odds| / (|Odds| + 100)
-150 → 150 / 250 = 60.0%
For positive odds: Implied probability = 100 / (Odds + 100)
+200 → 100 / 300 = 33.3%
The Vig
Add up both sides' implied probabilities and they'll exceed 100%. That excess is the sportsbook's margin.
Over -110 (52.4%) + Under -110 (52.4%) = 104.8%
The 4.8% overround is the cost of playing. On standard -110/-110 lines it's manageable. But some props get priced at -135/+105 where the vig jumps to ~8%. That wider margin demands a bigger edge to justify the bet.
Why This Matters for Props
Every prop bet is a comparison between two probabilities: the one the book is pricing in, and the one your data supports.
Say a sportsbook posts Jaylen Brown over 22.5 points at -110 (implied 52.4%). Your analysis of the matchup, recent form, and game environment puts him over at 58%. That's a 5.6% edge — a bet worth making. Not because you're certain he goes over, but because you're getting a price that undervalues the likelihood.
Our top-tier picks hit at 63.6% across 66 scored NBA picks. That kind of edge, applied consistently at standard juice, compounds into real profit over a season.
How Prop Juice Shifts
Player props don't always sit at -110/-110. The book adjusts based on where money flows and how confident they are in the number.
-110/-110 — Standard pricing. Lowest vig. Best spot for bettors.
-130/+110 — The book expects one side to hit more often. You need 56.5% to break even on the -130 side.
-150/+120 — Heavy juice. The market is screaming this outcome is likely, which means thin remaining value. Be cautious unless your data shows an even stronger edge.
-105/+105 or similar — The book isn't sure about the number. These are often the best spots for data-driven bettors because less information is priced in.
When a prop's juice shifts from -110/-110 to -125/+105 without the line moving, the book is signaling heavier action on one side. It's a quieter version of a line move.
Putting It Together
- Convert the odds. Know the break-even win rate before you look at the matchup.
- Build your probability estimate. Use matchup data, recent form, and game environment.
- Compare. If implied is 52% and your analysis says 58%, that's a real edge. If your analysis says 53%, the edge is too thin to overcome the vig — pass.
- Factor in the juice. A 3% edge at -110 is worth betting. A 3% edge at -150 is not.
- Track over time. One bet proves nothing. Two hundred bets tell you if your process works.
The edge isn't in understanding odds — that's just the framework. The edge is in the matchup data and game context that tell you when the market's implied probability is wrong. Check the Prop Analyzer to see where tonight's numbers don't add up.
Related: Betting Guides Hub for more betting guides coverage.
References & Tools
- Top Plays board
- Further reading: Pregame odds & probability primer (Investopedia)