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Convert American or decimal odds to implied probability and payout. Implied probability is the win rate the book's price assumes. Compare to your model's probability to find edge.
Convert American or decimal odds to implied probability. Implied probability is the win rate the book's price assumes. Compare it to your model's probability to identify edge.
For no-vig probability across both sides of a two-way market, use the devig calculator.
Every odds price corresponds to a probability the book is assuming. -150 implies the book thinks the side wins 60% of the time. +150 implies 40%. Convert to compare your model's probability to the book's belief.
Implied probability includes the book's vig. The true (no-vig) probability the market thinks is fair is lower. Example: at -110/-110, both sides imply 52.4%, summing to 104.8%. The 4.8% excess is the overround. The book's built-in margin works out to about 4.5% of each bet (1 - 1/1.0476). Divide each side by 1.048 to get the no-vig probability: 50.0% each. Use the devig calculator for two-way markets.
Your edge is your model's probability minus the no-vig market probability, but the bet is only +EV when your probability also beats the implied probability of the price you bet, vig included. If your model says 62% and the no-vig market is 58%, you have 4 percentage points of edge; at -150 (60% implied) that bet is +EV. Stake by Kelly criterion to size appropriately.
-300 → ~75% implied · payout $133 / profit $33 per $100-200 → ~67% implied · payout $150 / profit $50 per $100-150 → ~60% implied · payout $167 / profit $67 per $100-110 → ~52% implied · payout $191 / profit $91 per $100+100 → ~50% implied · payout $200 / profit $100 per $100+150 → ~40% implied · payout $250 / profit $150 per $100+200 → ~33% implied · payout $300 / profit $200 per $100Negative American odds (favorites): probability = abs(odds) / (abs(odds) + 100). Example: -150 → 60%. Positive American odds (underdogs): probability = 100 / (odds + 100). Example: +135 → 42.6%. Both include vig.
Implied probability is the win rate a sportsbook's price assumes. -150 implies 60%; +150 implies 40%. The book's vig means the implied probabilities on a two-way market sum to over 100% (typically 102-110%).
Sportsbook prices include vig (the book's commission). Implied probabilities on both sides of a market sum to over 100%, with the excess being the vig. True (no-vig) probability is implied probability divided by the total, removing the book's cut.
Decimal odds to implied probability: probability = 1 / decimal. Example: decimal 2.00 → 50%. Decimal 1.667 → 60%. Decimal 3.50 → 28.6%.
Both express the same price differently. American uses +/- format (-150 = bet $150 to win $100, +135 = bet $100 to win $135). Decimal expresses total payout per $1 (1.667 = $1.67 back per $1 bet, including stake). Decimal is easier for math; American is the US standard.