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How to Read Sports Betting Odds

Every Ohio sportsbook displays odds in American format by default, but most also support decimal and fractional formats. Understanding what the numbers mean — and how to convert between them — is the foundation of every sports bet.

American Odds

American odds use a plus or minus sign followed by a number. The minus sign indicates the favorite — the team or player expected to win. The plus sign indicates the underdog.

  • Negative odds (-150): Risk $150 to win $100. The number tells you how much you must wager to win $100 in profit.
  • Positive odds (+200): Wager $100 to win $200. The number tells you how much profit you win on a $100 stake.

Decimal Odds

Decimal odds (used widely in Europe and at international books like bet365) express the total return per $1 wagered. A 2.50 decimal line means a $100 wager returns $250 total ($150 profit plus your stake).

Conversion formulas:

  • Positive American to decimal: (Odds / 100) + 1. So +200 → (200/100) + 1 = 3.0.
  • Negative American to decimal: (100 / |Odds|) + 1. So -150 → (100/150) + 1 = 1.667.

Fractional Odds

Fractional odds (used mainly in UK horse racing) display profit-to-stake. 5/2 means a $2 stake wins $5 in profit, for a total return of $7. They're rare in Ohio sports betting but available at some sportsbooks for horse racing markets.

Implied Probability

Every odds line corresponds to an implied probability — the chance the bet wins, according to the sportsbook. To find value, you need to estimate the true probability and compare it to the implied probability.

  • +100 (even money): 50% implied probability
  • -150: 60% implied probability
  • +200: 33.3% implied probability
  • -300: 75% implied probability

If your model says a team should win 65% of the time and the line implies only 60%, that's a +EV bet — long-term profitable if your model is accurate.

The Vig (Juice)

Sportsbooks build margin into both sides of a market. A standard NFL spread is -110 / -110 (~52.4% implied probability per side, totaling 104.8%). The 4.8% extra is the sportsbook's edge — also called the vig, juice, or hold.

Sharp Ohio bettors look for reduced-juice promos (-105 or +100 lines) at DraftKings, FanDuel, and BetMGM. Even a 5-cent reduction in juice meaningfully improves long-term ROI.

FAQ

What does +200 mean?

A +200 American odds line means a $100 wager wins $200 in profit. The plus sign always indicates the underdog. Total return on a winning $100 bet at +200 is $300 (your stake plus your profit).

What does -150 mean?

A -150 American odds line means you must wager $150 to win $100 in profit. The minus sign always indicates the favorite. A $150 winning bet at -150 returns $250 total.

How do I convert American odds to decimal?

For positive odds: (Odds / 100) + 1. For example, +200 = 3.0. For negative odds: (100 / |Odds|) + 1. For example, -150 = 1.667.

What is implied probability?

Implied probability is the chance an outcome happens based on the odds. For -150, implied probability is 60%. For +200, it is 33.3%. Sportsbooks build a 4-5% margin into these probabilities.

Which odds format is best?

American odds are standard in Ohio. Decimal odds (used in Europe) make payout calculation faster: just multiply your stake by the decimal. Fractional odds (UK) are rare in US sports betting.