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How to Read Betting Odds | American, Decimal, Fractional

How to read betting odds starts with three formats—American, decimal, and fractional—and the core ideas of implied probability, favorite vs underdog, and payout. Once you can convert between formats, you’ll understand prices, compare books, and spot value faster. For a neutral background on odds formats, see Wikipedia: Odds.

American Odds (U.S.)

American odds use plus (+) and minus (−) numbers.

  • Favorites (−): The number shows how much you must risk to win $100. Example: −150 → risk $150 to win $100 (total return $250).
  • Underdogs (+): The number shows how much you win on a $100 stake. Example: +130 → risk $100 to win $130 (total return $230).

Implied Probability (American)

  • For favorites (−A): A / (A + 100). Example: −150 → 150 / 250 = 60%.
  • For underdogs (+A): 100 / (A + 100). Example: +130 → 100 / 230 ≈ 43.48%.

Payout (American)

  • Favorite (−A) with stake S: win = S × (100 / A); return = S + win.
  • Underdog (+A) with stake S: win = S × (A / 100); return = S + win.

Decimal Odds (EU)

One number includes your stake in the return: return = stake × decimal.

  • Example: 1.80 on $100 → return $180 (win $80).
  • Implied probability: 1 / decimal. Example: 1 / 1.80 = 55.56%.

Fractional Odds (UK)

Written as a/b and show profit relative to stake.

  • Example: 13/10 (≈ +130) means win $13 for every $10 staked (return $23 on $10).
  • Implied probability: b / (a + b). Example: 13/10 → 10 / 23 ≈ 43.48%.

Converting Between Formats

  • American → Decimal:

    −A → 1 + (100 / A); +A → 1 + (A / 100).

    Example: −150 → 1 + (100/150) = 1.6667; +130 → 1 + (130/100) = 2.30.
  • Decimal → American:

    If D ≥ 2.00 (underdog): +[(D − 1) × 100]; If D < 2.00 (favorite): −[100 / (D − 1)].

    Example: 1.80 → −125; 2.40 → +140.
  • Fractional ↔ Decimal: a/b → (a/b) + 1; Decimal D → (D − 1) as a fraction simplified.

Favorites vs Underdogs (At a Glance)

  • Favorite: Minus price (−). Higher probability, lower payout per dollar.
  • Underdog: Plus price (+). Lower probability, higher payout per dollar.

Break-Even Percentages (Common Prices)

  • −120 → 54.55%
  • −115 → 53.49%
  • −110 → 52.38%
  • −105 → 51.22%
  • +100 → 50.00%
  • +110 → 47.62%

Lower vig reduces break-even. See Vig and Juice Explained.

Examples (Single Bets)

Favorite Example

Stake $60 at −120 → win = 60 × (100/120) = $50; return $110. Implied probability 54.55%.

Underdog Example

Stake $80 at +150 → win = 80 × (150/100) = $120; return $200. Implied probability 40%.

Parlays (Quick Orientation)

Multiply decimal odds for each leg to estimate “fair” payout, then compare to the book’s offer. Multi-leg bets raise variance and effective hold—use small stakes. See Parlays, Teasers & Round Robins.

Common Mistakes

  • Confusing return with profit: Decimal shows total return; profit = return − stake.
  • Ignoring implied probability: Convert prices to % to compare value across formats.
  • Forgetting fees (vig): The price embeds bookmaker margin; shop multiple books. See How to Shop Betting Lines.

FAQs: How to Read Betting Odds

Which format should I use? Use whatever’s most comfortable. Decimal is quick for payouts; American is standard in the U.S.

Do American odds include my stake? No—American shows win amount; your return adds the stake back.

How do I compare −115 vs −110? Convert to implied probability (53.49% vs 52.38%) or decimal (1.8696 vs 1.9091). Lower break-even is better, all else equal.

Related Guides

Responsible Gaming

Bet responsibly. Set limits, track results, and seek help if betting stops being fun.