Before any stat matters, you need to read the price. American odds look intimidating but they answer one simple question: what does this bet imply about the chance of winning? Once you can convert odds to a probability, you can tell a good number from a bad one.
Table of Contents
Reading the minus and the plus
- Negative odds (−150) show how much you must stake to win $100. −150 means risk $150 to win $100 — a favorite.
- Positive odds (+130) show how much $100 wins. +130 means risk $100 to win $130 — an underdog.
Converting odds to implied probability
For a favorite: implied % = odds ÷ (odds + 100). So −150 → 150 ÷ 250 = 60%. For an underdog: implied % = 100 ÷ (odds + 100). So +130 → 100 ÷ 230 = 43.5%. This is the number that actually matters.
The vig, and why the numbers add up to more than 100%
Add both sides of a game and you’ll get something like 104–108%, not 100%. That extra is the sportsbook’s margin — the vig. It’s why beating the closing number matters: you’re not just beating the opponent, you’re beating the price plus the house edge.
Putting it to work
Every good bet comes down to one comparison: your estimate of the true probability versus the implied probability of the line. If a stat says a first-inning run is 58% likely and the price implies 54%, that’s an edge. If they match, there’s no bet. BetSlate runs this comparison on every card so you don’t have to do the math by hand.
