Reading American odds
- Minus (-) odds show how much you must risk to win $100. At -150, you risk $150 to win $100.
- Plus (+) odds show how much you win on a $100 bet. At +150, a $100 bet wins $150.
- +100 (also called even money) means you win the same amount you risk.
Favorite -150 · Underdog +130
A $50 bet on the favorite wins $33.33 profit (50 × 100 ÷ 150). A $50 bet on the underdog wins $65 profit (50 × 130 ÷ 100). If you win, you also get your $50 back.
Other odds formats
The same price can be written three ways:
| American | Decimal | Fractional | Implied probability |
|---|---|---|---|
| -200 | 1.50 | 1/2 | 66.67% |
| -110 | 1.91 | 10/11 | 52.38% |
| +100 | 2.00 | 1/1 (evens) | 50.00% |
| +150 | 2.50 | 3/2 | 40.00% |
| +300 | 4.00 | 3/1 | 25.00% |
- Decimal odds show your total return per $1, including your stake. 2.50 means a $10 bet returns $25 ($15 profit plus your $10).
- Fractional odds show profit relative to stake. 3/2 means $3 profit for every $2 risked.
Implied probability
Implied probability turns a price into the win rate you'd need to break even at that price.
Minus odds: implied probability = odds ÷ (odds + 100), using the number without the minus sign. -110 → 110 ÷ 210 = 52.38%.
Plus odds: implied probability = 100 ÷ (odds + 100). +150 → 100 ÷ 250 = 40%.
Decimal odds: implied probability = 1 ÷ decimal odds. 2.50 → 40%.
The odds converter does all of these conversions for you.
Spotting the vig
Add up the implied probabilities of every side of a market. In a fair market, they'd total exactly 100%. Sportsbooks build in a margin (the vig), so the total comes out higher.
-110 / -110: 52.38% + 52.38% = 104.76%. The extra 4.76% is the book's built-in margin.
-150 / +130: 60.00% + 43.48% = 103.48%. Remove the margin by dividing each side by the total: about 57.98% and 42.02%. That's the "no-vig" estimate of each side's chance.
Price vs. probability
A bet only makes sense in the long run if you believe the true chance of winning is higher than the implied probability of the price you're getting. That's hard to do consistently, and the vig means most bettors lose money over time. Getting a better price on the same bet (for example, +140 at one book vs. +130 at another) lowers the win rate you need, which is why comparing books matters.
Quick recap. Minus = risk that much to win $100. Plus = win that much on $100. Implied probability is the break-even win rate. Add both sides together to see the vig.
Education only. Not betting advice. 21+.