How Do Betting Odds Work?
Your complete guide to understanding betting odds
7 min read
The Quick Answer
Betting odds tell you two things: the probability of an outcome and how much you can win.
Negative odds (-150) show how much you bet to win $100. Positive odds (+150) show how much you win on a $100 bet. The odds also imply probability—-150 suggests a 60% chance, +150 suggests a 40% chance.
The Three Odds Formats
There are three main ways to express betting odds. They all represent the same thing—just written differently.
American Odds
Most common in the US.
• -150: Bet $150 to win $100
• +150: Win $150 on $100 bet
Also called "moneyline odds"
Decimal Odds
Popular in Europe/Australia.
• 1.67: Same as -150
• 2.50: Same as +150
Multiply stake × odds = total return
Fractional Odds
Traditional UK format.
• 2/3: Same as -150
• 3/2: Same as +150
Profit/Stake ratio
Need to convert between formats? Use our Odds Converter.
Odds Conversion Chart
| American | Decimal | Fractional | Implied Prob. | What It Means |
|---|---|---|---|---|
| -200 | 1.50 | 1/2 | 66.7% | Bet $200 to win $100 |
| -150 | 1.67 | 2/3 | 60% | Bet $150 to win $100 |
| -110 | 1.91 | 10/11 | 52.4% | Bet $110 to win $100 |
| +100 | 2.00 | 1/1 | 50% | Bet $100 to win $100 |
| +150 | 2.50 | 3/2 | 40% | Bet $100 to win $150 |
| +200 | 3.00 | 2/1 | 33.3% | Bet $100 to win $200 |
| +300 | 4.00 | 3/1 | 25% | Bet $100 to win $300 |
How to Calculate Payouts
Negative Odds Formula
Profit = (Stake × 100) ÷ |Odds|
Example: $50 bet at -150
Profit = ($50 × 100) ÷ 150 = $33.33
Total Return = $50 + $33.33 = $83.33
Positive Odds Formula
Profit = (Stake × Odds) ÷ 100
Example: $50 bet at +200
Profit = ($50 × 200) ÷ 100 = $100
Total Return = $50 + $100 = $150
Skip the math—use our EV Calculator for instant calculations.
Understanding Implied Probability
Implied probability is the win percentage that odds suggest. This is crucial for finding value bets.
Converting Odds to Probability
Negative odds: |Odds| ÷ (|Odds| + 100)
Positive odds: 100 ÷ (Odds + 100)
Example: -150 → 150 ÷ 250 = 60%
Why This Matters
If you think a team has a 70% chance of winning but the odds only imply 60%, that's a value bet.
Finding spots where your estimate beats the implied probability is how sharps profit.
Learn more: What is Expected Value?
Why Do Odds Change?
Lines move constantly. Understanding why can help you time your bets better.
Betting Volume
When lots of money comes in on one side, books adjust odds to balance their liability and encourage action on the other side.
Sharp Action
When professional bettors (sharps) bet, books move lines quickly. These "steam moves" signal informed money.
Injuries & News
A star player injury, coaching change, or weather report can shift odds dramatically within minutes.
Market Consensus
As game time approaches, lines typically sharpen and settle toward their "true" market price.
Related: Line Movement | Steam Moves
Now That You Understand Odds...
Find bets where the true probability beats the implied odds. Get 5 free +EV picks daily.
Frequently Asked Questions
How do betting odds work?
Betting odds show the probability of an outcome and how much you can win. Positive odds (+150) show profit on a $100 bet, negative odds (-150) show how much you must bet to win $100. Lower odds mean higher probability, higher odds mean lower probability.
What do negative odds mean?
Negative odds (like -150) indicate the favorite. The number shows how much you must bet to win $100. At -150, you bet $150 to win $100 profit. The larger the negative number, the heavier the favorite.
What do positive odds mean?
Positive odds (like +200) indicate the underdog. The number shows how much profit you win on a $100 bet. At +200, a $100 bet wins $200 profit. The larger the positive number, the bigger the underdog.
How do I calculate my payout from odds?
For positive odds: (Stake × Odds) / 100 + Stake = Payout. For negative odds: (Stake × 100) / |Odds| + Stake = Payout. Example: $50 at +200 = $150 total ($100 profit + $50 stake).
Why do odds change?
Odds change based on betting action, injuries, weather, and new information. When money comes in on one side, books adjust odds to balance their risk. Sharp bettors moving lines can signal valuable betting opportunities.