Core Formulas
American positive: 100 ÷ (odds + 100)
American negative: |odds| ÷ (|odds| + 100)
Decimal: 1 ÷ decimal odds
BETTING MATH GUIDE
Implied Probability Betting Guide
If you only learn one concept in betting, learn this one. Implied probability translates odds into the break-even win rate you need. Once you compare that number to your own projection, you can quickly identify value and avoid poor prices.
Quick Process
- Convert market odds to implied probability.
- Estimate your own win probability from data/context.
- Bet only when your estimate is meaningfully higher than market break-even.
- Apply bankroll discipline (flat stake or Kelly fraction).
Reference Examples
American -110
52.4%
Common spread/total pricing.
American +150
40.0%
Underdog needs to win 4/10 to break even.
Decimal 2.50
40.0%
Use 1 ÷ decimal odds.