How to Read Betting Odds

Betting odds look like a foreign language until someone explains the two simple rules behind them. Once you can read a line and turn it into a probability, you stop guessing and start seeing whether a bet is actually worth making.

American odds, explained

In the U.S., odds are shown as a number with a plus or minus sign:

• Minus (−) = favorite. The number is how much you must stake to win $100. At −200, you risk $200 to win $100.
• Plus (+) = underdog. The number is how much you win on a $100 stake. At +150, you risk $100 to win $150.

The bigger the minus number, the heavier the favorite. The bigger the plus number, the longer the underdog. A −110 line — the standard price on a point spread — means you risk $110 to win $100.

Converting odds to implied probability

Every line is really a probability in disguise. Implied probability is the win rate a bet needs just to break even at those odds.

For a favorite (minus odds): probability = odds ÷ (odds + 100).

−200 → 200 ÷ 300 = 66.7%. A −200 bet has to win two times out of three just to break even.

For an underdog (plus odds): probability = 100 ÷ (odds + 100).

+150 → 100 ÷ 250 = 40%. A +150 bet only needs to win 40% of the time to break even.

Quick reference:

• −110 → 52.4%
• −150 → 60.0%
• −200 → 66.7%
• +100 (even) → 50.0%
• +150 → 40.0%
• +250 → 28.6%

The vig hidden in every line

Here's the trick the numbers hide. On a coin-flip game, the book posts both sides at −110. Each side implies 52.4% — so the two sides add up to 104.8%, not 100%. That extra 4.8% is the vig (also called juice): the book's built-in cut, collected no matter who wins.

That's why beating the break-even number matters so much. At −110 you don't need to win half your bets — you need to win 52.4%, and every point above that is profit. The vig is the headwind on every ticket.

Implied vs true probability — where edges live

Implied probability tells you what the book thinks (plus its cut). The money question is whether the book is right. If a team's true chance of winning is 50% but the book is paying +150 (40% implied), you're getting paid like a 40% shot to win a 50% bet. That's a mispriced line — and it's exactly where profit comes from.

Knowing what the price should be is the job of a true line. Compare the true probability to the implied probability, and the gap is your expected value.

One more habit: line shopping

The same game is priced differently at different books. −105 instead of −110 doesn't look like much, but over a season it's the difference between winning and losing. Reading odds well includes shopping for the best number — the one piece of free edge available to everyone.