Why Convert Odds?
American, decimal, and fractional odds are three different notations for the exact same price. American odds (moneyline) are standard at U.S. sportsbooks, decimal odds are standard in Europe and on betting exchanges, and fractional odds are standard in the UK and Ireland. Knowing how to convert between them — and to implied probability — lets you compare prices across books regardless of which format each one displays, which is the foundation of line shopping.
Implied probability is what a given price suggests the win chance is, before removing the sportsbook's vig. Comparing your own probability estimate against implied probability is the basis of expected value — see the EV calculator to take that step.
Calculator
Enter a value in any one field below — the rest update live.
Common Odds Reference Table
Quick lookup for frequently seen prices:
| American | Decimal | Fractional | Implied Probability |
|---|
Format Reference
- American (moneyline): negative numbers show how much you must stake to win $100 (e.g. -110 = stake $110 to win $100); positive numbers show how much you win on a $100 stake (e.g. +150 = win $150 on $100).
- Decimal: total return per $1 staked, including your original stake. A decimal odds of 2.50 returns $2.50 for every $1 bet ($1.50 profit + $1 stake back).
- Fractional: profit relative to stake. 5/1 means $5 profit per $1 staked; 1/5 means $1 profit per $5 staked (a heavy favorite).
- Implied probability: what the price suggests the true win chance is, including the sportsbook's vig. Always divide 1 by the decimal odds to get this figure.
How Olympus Bets Uses Odds Data
Olympus Bets ingests live odds from sportsbook APIs across all 12 covered leagues and normalizes them to a single internal format before any model comparison happens:
- Live odds ingestion pulls current lines across major sportsbooks
- Normalization converts every price to decimal internally so model probabilities and market prices compare on the same scale
- Monte Carlo simulation produces an independent win/cover/total probability for comparison against the market-implied number
- Edge detection flags games where the calibrated model probability diverges meaningfully from the market-implied probability
- Line shopping logic checks whether a better price exists elsewhere before finalizing a recommendation
Further Reading
- Expected Value in Sports Betting: Full Guide — how implied probability feeds EV calculations
- Sharp vs. Square Money — how sharp bettors use odds movement and line shopping
- EV Calculator — turn implied probability and your own estimate into expected value
- CLV Calculator — measure whether you beat the closing line
- Kelly Criterion Calculator — convert an edge into an optimal bet size
- Our Methodology — full technical overview of the Olympus Bets platform