Understanding Betting Odds
Odds represent the relationship between the payout and the probability that a sportsbook assigns to an event. There are three major formats: American (moneyline), Decimal, and Fractional — and all three express the same information, just differently.
Odds Conversion Quick Reference
| American | Decimal | Fractional | Implied Probability | $100 Payout |
|---|
| -400 | 1.25 | 1/4 | 80.0% | $125 |
| -200 | 1.50 | 1/2 | 66.7% | $150 |
| -150 | 1.67 | 2/3 | 60.0% | $167 |
| -110 | 1.91 | 10/11 | 52.4% | $191 |
| +100 | 2.00 | 1/1 | 50.0% | $200 |
| +110 | 2.10 | 11/10 | 47.6% | $210 |
| +150 | 2.50 | 3/2 | 40.0% | $250 |
| +200 | 3.00 | 2/1 | 33.3% | $300 |
| +400 | 5.00 | 4/1 | 20.0% | $500 |
Which Odds Format Should You Use?
American
US sportsbooks
DraftKings, FanDuel, BetMGM, Caesars — standard in the US for all sports markets.
Decimal
Europe, Canada, Australia
Easier for parlay math — multiply all decimals together to get total parlay odds instantly.
Fractional
UK horse racing
Traditional format. Profit/stake ratio. 5/1 means $5 profit per $1 staked.
The Vig (House Edge)
Sportsbooks don't offer true odds — they add a margin called the vig or juice. At -110 on both sides, the implied probabilities sum to 104.8% (52.4% + 52.4%), meaning the book expects to keep 4.8% of all money wagered. This is why shopping for the best odds matters: getting +100 instead of -110 on a 50/50 bet eliminates the vig entirely.
Why Odds Shopping Matters
Over 1,000 bets at -110 vs +100 on the same 50/50 markets: at -110 you'd expect to lose ~$4,800 due to vig. At +100 you'd break even. This is why serious bettors use 3–5 different sportsbook accounts to always get the best available price. Use our odds converter to compare lines across books before locking in any bet.