How to Read American Odds (-150, +130, and What the Book Keeps)

Open any U.S. sportsbook and you'll see numbers like -150 and +130. They look like temperature readings. They're not. They're a compact way of telling you two things at once: who the favorite is, and how much the bet pays. Once you can read them, every other piece of betting math gets easier.

The two signs

The plus and minus signs split every odds quote into two camps:

• Minus odds (e.g. -150) mean a favorite. You have to risk more than $100 to win $100 in profit. The number tells you how much. At -150, you risk $150 to profit $100.
• Plus odds (e.g. +130) mean an underdog. A $100 bet wins more than $100. The number tells you how much. At +130, a $100 bet wins $130 in profit.

That's the whole rule. Everything else is just plugging different numbers into the same shape.

A worked example

Imagine the Yankees are playing the Red Sox tonight. The sportsbook shows:

Read across one row at a time. The Yankees are -150: they're the favorite, and you have to put up $150 to win $100. Implied probability: 60%. The Red Sox are +130: they're the underdog, and a $100 bet returns $130 profit. Implied probability: about 43.5%.

Notice anything? Add the two implied probabilities: 60% + 43.5% = 103.5%. That extra 3.5% is not a math error. It's the sportsbook's margin - the vig. We'll cover that in detail in the next chapter, but the takeaway here is that the numbers you see on the screen always add to slightly more than 100%, because the book is keeping a cut.

How to convert odds to a probability in your head

You don't need a calculator. Two formulas, one for each sign:

• Minus odds: divide the number by (the number + 100). Example: -150 → 150 / 250 = 60%.
• Plus odds: divide 100 by (the number + 100). Example: +130 → 100 / 230 ≈ 43.5%.

With practice you'll start to recognize the common ones without thinking:

Why this matters before you bet

Implied probability is the price the book is asking for the outcome. If you think the Yankees have a 65% chance to win and the book is pricing them at 60%, you have an edge. If you think they have a 55% chance and the book is pricing them at 60%, the book has an edge over you. Without converting odds to probability, you can't actually tell those two situations apart - they both feel like "I like the Yankees."

Almost every concept later in the guide - vig, line shopping, expected value, closing line value - depends on this conversion. It's the foundation. Get fluent with it.

Same bet, three formats

The same bet looks different depending on where you are. The math doesn't change; only the display does:

• American (U.S. default): -150 / +130. Built around $100 as the unit.
• Decimal (European default): 1.67 / 2.30. Multiply your stake by the decimal to get total return (stake + profit).
• Fractional (UK default): 2/3 / 13/10. The numerator is your profit per "denominator" of stake.

Most sportsbooks let you toggle the format in your account settings. If American odds feel awkward, decimal often clicks faster - total return is just stake × decimal.

What about totals and run lines?

The same odds format applies to every bet on the board. A total of "Over 8.5 (-110)" means you're risking $110 to win $100 that the game will end with 9 or more total runs. A run line of "Yankees -1.5 (+140)" means you're risking $100 to win $140 that the Yankees will win by 2 or more. The bet type changes; the way odds work doesn't.

We'll meet each of those bet types properly in Part 3. For now, you have the only piece of math you actually need to read any line on any sportsbook.