Strip the sportsbook's vig out of any 2-way or 3-way market. Enter both sides' American odds; the calculator returns the fair (no-vig) probabilities. Use no-vig probability as the baseline for edge identification.
Paste both sides of a two-way market (or three sides of a three-way market). The calculator strips the sportsbook's vig and returns the no-vig (fair) probabilities the market thinks. No-vig probability is what you compare your model against to find edge.
Sportsbook prices include vig — the book's built-in commission. When you add both sides of a two-way market, the implied probabilities sum to MORE than 100% (typically 102-110%). The extra is the vig. To find the fair probability the market actually thinks, divide each side's implied probability by the total. That removes the vig.
Market: Yankees -150 vs Red Sox +130.
The market thinks the Yankees win 58.0% of the time, not 60.0%. The 2 percentage points were vig.
Your bet has edge when your win probability estimate exceeds the no-vig market probability by 3+ percentage points. Example: your model says Yankees 62%; no-vig market says 58%; your edge is 4 points. The bet is +EV at -150. Size with the Kelly calculator.
Lower vig means better prices for you. Line-shopping across 3+ books captures small no-vig probability advantages on every pick.
Some markets (soccer, hockey 3-way) have three outcomes: home win, draw, away win. The calculator handles 3-way: enter all three sides' American odds and the math divides each by the total to give no-vig probabilities for all three.