How Do Betting Odds Work? American Odds Explained Simply
What -110, +150, and -200 actually mean, how to convert odds to implied probability, and why the difference between odds and probability is where all the money is.
The 30-second version
American odds answer one question: how much do I win relative to $100? Negative odds (-110, -200) tell you how much you must risk to win $100. Positive odds (+150, +300) tell you how much you win if you risk $100. That's the whole system.
So -110 means risk $110 to win $100. +150 means risk $100 to win $150. A -200 favorite means the book thinks that side wins a lot more often than not — you're paying a premium price for a likely outcome.
Odds are really probabilities in disguise
Every price converts to an implied win probability. For negative odds: probability = odds / (odds + 100), using the odds as a positive number. So -110 implies 110/210 = 52.4%, and -200 implies 200/300 = 66.7%. For positive odds: probability = 100 / (odds + 100). So +150 implies 100/250 = 40%, and +300 implies 25%.
This is the single most useful conversion in betting. When you see +150, stop thinking "I win $150" and start thinking "the market says this happens 40% of the time." The question that matters is never the payout — it's whether the true probability is higher or lower than the implied one.
Why both sides are -110: the vig
A fair coin flip should be +100 both ways. Sportsbooks post -110/-110 instead. Add the implied probabilities: 52.4% + 52.4% = 104.8%. That extra 4.8% is the vig (or juice) — the book's built-in fee. It means a spread bettor must win about 52.4% of the time just to break even, not 50%.
The vig is why picking more winners than losers isn't enough to profit, and why line shopping matters: getting -105 instead of -110 sounds trivial but cuts the tax you pay on every single bet.
Reading a real board
Take an MLB game: Yankees -160, Rays +140. The book implies the Yankees win 61.5% of the time and the Rays 41.7%. Those add to over 100% — the overlap is the vig. Remove it proportionally and the market's true opinion is roughly 60/40.
A bet on either side is a claim that the market's number is wrong. If you think the Rays win 45% of the time, +140 (41.7% implied) is a good bet even though the Rays probably lose. That's the mental shift that separates betting from picking winners: you're not predicting the game, you're pricing it.
Frequently asked questions
What does -110 mean in betting?
You must risk $110 to win $100. It implies a 52.4% probability and includes the sportsbook's fee (the vig).
Is + or - better in betting odds?
Neither is inherently better. Negative odds mean a likelier outcome with a smaller payout; positive odds mean a less likely outcome with a bigger payout. Value depends on whether the true probability beats the implied one.
How do I convert American odds to probability?
Negative odds: odds/(odds+100) using the absolute value, so -150 → 150/250 = 60%. Positive odds: 100/(odds+100), so +200 → 100/300 = 33.3%.
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