American vs. Decimal vs. Fractional Odds: Converting Between Formats
Bikash Roy
Online Research Specialist · SEO Strategist · Web Developer
Bikash personally verifies every calculator against official standards (WHO, NIH, government data). Online research specialist, SEO strategist, and web developer with 10+ years building accurate digital tools.
Full bio →The same bet gets quoted differently depending on the sportsbook and the region — American odds dominate US books, decimal odds are standard across most of Europe and Australia, and fractional odds remain common in the UK and Ireland. All three describe the exact same underlying probability.
American Odds
Shown as a positive or negative number relative to a $100 bet. Negative odds show the stake needed to win $100 (e.g., -150 means bet $150 to win $100); positive odds show the payout on a $100 bet (e.g., +130 means bet $100 to win $130). This is the format the no-vig calculator uses directly.
Converting American to Decimal Odds
Positive American odds: Decimal = (American ÷ 100) + 1
Negative American odds: Decimal = (100 ÷ |American|) + 1Example: +130 American odds → (130 ÷ 100) + 1 = 2.30 decimal
Example: -150 American odds → (100 ÷ 150) + 1 = 1.67 decimal
Decimal odds represent the total payout (including your original stake) per $1 wagered — a 2.30 decimal means a $10 bet returns $23.00 total ($13.00 profit plus your $10 stake back).
Converting Decimal to Fractional Odds
Fractional = (Decimal − 1), expressed as a fractionExample: 2.30 decimal → 2.30 − 1 = 1.30 → approximately 13/10 fractional
Example: 1.67 decimal → 1.67 − 1 = 0.67 → approximately 2/3 fractional
Fractional odds represent profit only relative to the stake — 13/10 means a $10 bet profits $13 (plus the original $10 stake returned), matching the same total payout as the 2.30 decimal example above.
Converting Directly From American to Fractional
Positive American odds: Fractional = American / 100
Negative American odds: Fractional = 100 / |American|Example: +130 → 130/100, simplified to 13/10 Example: -150 → 100/150, simplified to 2/3
Why the No-Vig Math Works the Same Underneath All Three
Implied probability is what actually drives the no-vig calculation, and every odds format converts to the same implied probability for the same true likelihood — the format is just a different way of presenting the identical underlying number. If you’re working from decimal or fractional odds instead of American, convert to American first using the reverse of the formulas above, then use the no-vig calculator as normal. See the sports betting odds glossary for how implied probability itself is calculated from American odds.
A Quick Reference Table
| American | Decimal | Fractional | Implied Probability |
|---|---|---|---|
| -200 | 1.50 | 1/2 | 66.67% |
| -110 | 1.91 | 10/11 | 52.38% |
| +100 | 2.00 | 1/1 | 50.00% |
| +150 | 2.50 | 3/2 | 40.00% |
| +300 | 4.00 | 3/1 | 25.00% |
Practical Reason to Know All Three
If you’re comparing odds across an international sportsbook (decimal) against a US book (American) for the same event, converting both to the same format — or straight to implied probability — is the only way to make an apples-to-apples comparison. See using no-vig odds to find value bets for how this comparison fits into finding the best available price on a specific bet.
References & Sources
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