Field guide
Odds without the fog
Prices, implied probability, vig, and why line shopping changes the math.
9 min read · Updated August 2026
01
The price is part of the bet
American odds express both payout and implied probability. At -110, a bettor risks 110 to profit 100; at +150, a 100 risk returns 150 profit. Comparing selections without prices hides a meaningful part of the decision.
02
Implied probability
For positive American odds, implied probability is 100 / (odds + 100). For negative odds, it is |odds| / (|odds| + 100). These are market-implied values before removing the bookmaker margin.
03
Vig and fair probability
Opposing implied probabilities commonly total more than 100%. The excess is the market margin. A no-vig estimate normalizes both sides so their probabilities sum to 100%, but it remains a market estimate—not ground truth.
04
Line shopping
A half-point, a better moneyline, or reduced juice changes expected value. Always compare the exact market and timestamp; stale or mismatched lines produce misleading comparisons.