Odds → Probability: American Odds Made Simple

American odds are weird. To the uninitiated, seeing numbers like -110 or +240 looks more like an algebra problem than a price tag. But here’s the secret: they are just probabilities in disguise.

If you are betting based on the plus and minus signs, you are playing the sportsbook’s game. If you translate those odds into percentages, you are playing math. And math is the only way to win long-term.

American odds make it easy to think in payouts, but harder to think in probability. Your job is to strip away that confusion and see the raw probability underneath. Once you start thinking in percentages rather than payouts, you stop guessing and start investing. Let’s break the code.

Why Convert American Odds to Probability?

American odds tell you how much you win, but they don’t explicitly tell you how likely you are to win. That’s a problem.

To find value—real, mathematical edge—you need to compare two numbers:

1. Implied Probability: The chance of winning that the sportsbook’s odds suggest.
2. True Probability: The actual chance of winning based on your data and models.

If your true probability is higher than the implied probability, you have a +EV (Expected Value) bet. But you can't make that comparison if you can't read the language. Converting odds to implied probability is the first step in spotting when the market is wrong.

Quick note: implied probability usually includes the sportsbook's vig, so it's not a "true" probability. To estimate a market-fair probability, remove the vig.

How to Convert American Odds to Probability

The formula changes slightly depending on whether the odds are positive (+) or negative (-). Don’t worry; you don’t need a calculus degree. Just a calculator.

Converting Positive Odds (+)

Positive odds (e.g., +120, +200) show how much profit you make on a $100 bet. They usually indicate the underdog or a less likely outcome (less than 50%).

The Formula:

Implied Probability = 100 / (Odds + 100)

Example: Converting +120
Let's say you're looking at an underdog priced at +120.

1. Add the odds to 100:

   120 + 100 = 220

2. Divide 100 by that result:

   100 / 220 = 0.4545

3. Convert to percentage:

   45.45%

The Insight: When a book gives you +120, they are saying, "We think this happens roughly 45% of the time." If your model says it happens 50% of the time, you have an edge.

Converting Negative Odds (-)

Negative odds (e.g., -150, -240) show how much you must bet to win $100. These are usually the favorites.

The Formula:

Implied Probability = Absolute Odds / (Absolute Odds + 100)

(Note: "Absolute" just means ignoring the minus sign. Treat -150 as 150.)

Example: Converting -150
You want to bet on a favorite priced at -150.

1. Add the absolute odds to 100:

   150 + 100 = 250

2. Divide the absolute odds by that result:

   150 / 250 = 0.60

3. Convert to percentage:

   60.00%

The Insight: At -150, the market implies a 60% win rate. If you think the team only has a 55% chance to win, this is a bad bet—even if they are the "better" team.

Understanding Break-Even Percentage

Implied probability is the break-even win rate for that price.

If you bet on -110 odds exclusively, you need to win 52.38% of your bets just to end up with $0.00 profit. That is your hurdle rate.

• If your win rate is higher than the break-even percentage, you are profitable.
• If your win rate is lower, you are donating to the sportsbook’s light bill.

Many bettors think 51% makes them sharp. At -110, it’s still negative ROI — you’re risking $110 to win $100, which is why you need 52.38% to break even. Knowing the break-even percentage keeps you honest. It forces you to ask: "Do I really win this bet often enough to justify the price?"

Quick Reference Table: The Cheat Sheet

Don’t want to run the math every time the line moves? Keep this table handy. It covers the most common lines you’ll see in the NFL, NBA, and MLB.

Break-even win rate for each price (before no-vig conversion or line shopping).

Note: As the payouts get higher (positive odds), the required win rate drops. As the price gets steeper (negative odds), you need to be right much more often.

Line shopping matters: moving from -110 to -105 lowers your break-even rate and increases long-run ROI.

Stop Guessing, Start Calculating

If your "gut feeling" isn’t backed by data, it’s just heartburn. Sports betting isn't about picking winners; it's about buying probability at a discount.

Now that you can convert American odds to probability, you can spot when a sportsbook’s price is off. But doing this manually for every game on the slate is slow, and speed is currency in this market.

Ready to automate your edge?

Don't waste time punching numbers into a calculator. Use our EV Calculator to instantly identify +EV opportunities where the probability is in your favor. Then, head over to the Betting Lines page to ensure you're always grabbing the best price available.

The book builds the stadium. We just mark where the blueprint is wrong.

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Odds & Probability FAQ

What is implied probability?
Implied probability translates betting odds into a percentage chance of an event happening, according to the bookmaker’s price.

What is break-even percentage?
Break-even percentage is the win rate you need to hit zero profit at a given set of odds. If your win rate is higher, you’re profitable. Lower, you're giving money to the house.

Why do both sides add to more than 100%?
Because the sportsbook bakes in the vig (their cut), so the total implied probability typically exceeds 100%. The overage is their edge.

What’s the fastest way to convert odds to probability?
Use these shortcuts:

+ odds → 100 / (odds + 100)

and

- odds → abs(odds) / (abs(odds) + 100)

. Or, use our Implied Probability Calculator to do the conversion instantly.

Meta Information

Meta Title: Convert American Odds to Probability (Free Cheat Sheet)
Meta Description: Learn how to convert American odds to implied probability, break-even percentage, and understand the impact of the vig. Stop guessing and start finding mathematical value in your bets.