odds to percent calculator

What this odds to percent calculator does

This calculator converts betting odds into implied probability, shown as a percentage. Implied probability answers a simple question: what chance of winning is built into these odds? It works with the three most common formats used by sportsbooks:

• Decimal odds (common in Europe, Canada, and many online books)
• Fractional odds (traditional UK format, like 5/1 or 7/2)
• American odds (moneyline, like +150 or -120)

Odds to probability formulas

1) Decimal odds → percent

Formula: Probability (%) = (1 / Decimal Odds) × 100

Example: Decimal odds of 2.50 gives (1 / 2.50) × 100 = 40%.

2) Fractional odds → percent

Fractional odds are written as A/B. Formula: Probability (%) = B / (A + B) × 100

Example: 5/2 gives 2 / (5 + 2) × 100 = 28.57%.

3) American odds → percent

American odds use positive and negative numbers:

• For positive odds (+A): Probability (%) = 100 / (A + 100) × 100
• For negative odds (-A): Probability (%) = A / (A + 100) × 100 where A is the absolute value

Example: +200 implies 33.33%; -150 implies 60.00%.

Why implied probability matters

Odds alone can be hard to compare across formats. Converting everything to percentages makes decisions clearer:

• Compare prices from multiple sportsbooks quickly
• Check whether your own projection is higher or lower than market probability
• Identify value bets when your estimated true chance exceeds implied probability

Common mistakes to avoid

• Using decimal odds below 1.00 (invalid for standard betting odds)
• Forgetting the plus/minus sign in American odds
• Confusing fractional odds (profit/stake) with direct win probability
• Assuming implied probability equals true probability without considering sportsbook margin

A note on sportsbook margin (vig)

Implied probability from listed odds usually includes bookmaker margin. In two-way markets, both sides may sum to more than 100%. If you want a “fair” probability estimate, you need to remove that overround. This tool focuses on direct conversion of a single quoted odd.

FAQ

Is 50% the same as even odds?

Yes. 50% corresponds to decimal 2.00, fractional 1/1, and American +100.

Can I type fractional odds with a colon?

Yes. You can enter 3/1 or 3:1 in this calculator.

What does a higher implied probability mean?

A higher implied probability means the event is priced as more likely to happen. Favorites have higher implied percentages; underdogs have lower ones.