Before you place a single bet, you need to read the number next to it correctly. Betting odds tell you two things: how much a bet pays, and what probability the book is implying. This is a plain-English guide to the three formats and the “juice” hidden in every line. It is not betting advice — we explain the math, not what to pick.
American odds (+150 / −110)
The US default. A positive number is profit on a $100 stake: +150 means a $100 bet wins $150 profit ($250 back). A negative number is how much you must stake to win $100: −110 means you stake $110 to win $100. Favourites are negative, underdogs positive.
Decimal odds (2.50)
Common outside the US and on crypto books. The number is your total return per $1 staked, including your stake. At 2.50, a $100 bet returns $250 ($150 profit). Decimal is the easiest format for comparing value quickly.
Fractional odds (3/2)
Traditional UK format. The fraction is profit-to-stake: 3/2 means $3 profit for every $2 staked. So $100 returns $150 profit ($250 total). Less common online, but you will see it.
Implied probability — and how to convert it
Every line implies a probability. The quick conversions:
- Decimal: probability = 1 ÷ odds. So 2.50 implies 1 ÷ 2.50 = 40%.
- Positive American: 100 ÷ (odds + 100). So +150 implies 100 ÷ 250 = 40%.
- Negative American: odds ÷ (odds + 100). So −110 implies 110 ÷ 210 ≈ 52.4%.
If your own estimate of an outcome’s chance is higher than the implied probability, the line is in your favour; if lower, it is not. That is the entire logic of value — without telling you which side to take.
What is the juice (vig)?
Notice that a standard two-way market is priced at −110 / −110, not +100 / +100. Each side implies about 52.4%, which adds to roughly 105% — not 100%. That extra ~5% is the juice (also called vig or margin): the book’s built-in edge. Lower juice means more of your money stays in play over time, which is why payout terms matter.
A worked example
Say you stake $50 on a team at +150. Profit = $50 × (150 ÷ 100) = $75, for $125 returned. The same line in decimal would be 2.50: $50 × 2.50 = $125 total. Same bet, same payout, two formats.
Odds are not advice
Reading odds well helps you understand price and probability. It does not predict winners, and nothing here is a betting tip. Bet only what you can afford to lose. For where these lines live, see our sportsbook reviews and the sports betting hub; to compare book types, read offshore vs regulated sportsbooks.
Frequently Asked Questions
What does −110 mean?
You stake $110 to win $100 profit. It is the standard price on a two-way market and bakes in the book’s juice.
Which odds format is best?
None is “best” — they express the same thing. Decimal is easiest for comparing value; American is the US default.
How do I calculate implied probability?
For decimal odds, divide 1 by the odds. For example, 1 ÷ 2.00 = 50%.
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