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How Sports Betting Odds Work

The three formats

Sports betting uses three odds formats. American odds (used in the US), decimal (Europe/Australia), and fractional (UK). BetIQ always shows American odds.

American-110 / +150
Decimal1.91 / 2.50
Fractional10/11 / 3/2

Reading American odds

Negative odds (e.g. -110) tell you how much you need to bet to win $100. Bet $110 to win $100 profit.

Positive odds (e.g. +150) tell you how much you win on a $100 bet. Bet $100 to win $150 profit.

Bet $110 at -110Win $100 → total $210 back
Bet $100 at +150Win $150 → total $250 back

Implied probability

Every set of odds implies a win probability. This is the market's estimate of how likely an outcome is.

For negative odds: implied prob = |odds| ÷ (|odds| + 100). For -110: 110 ÷ 210 = 52.4%

For positive odds: implied prob = 100 ÷ (odds + 100). For +150: 100 ÷ 250 = 40%

The vig (juice)

Notice that -110 implies 52.4% for both sides of a spread. That adds up to 104.8% — not 100%. The extra 4.8% is the book's margin (the vig). This is how sportsbooks profit regardless of outcome.

Line shopping (comparing across books) directly cuts into the vig and is the single best way to improve your results. BetIQ shows you where the best price is on every game.

Next: Expected Value Betting →