Implied Probability & Vig Remover
See the raw implied probability of each side, then strip out the sportsbook's margin to estimate a fair price.
Implied A
52.38%
Implied B
52.38%
Total (hold)
4.76%
Fair probability A (no-vig)
50.00%
Fair probability B (no-vig)
50.00%
A two-way market with no margin would sum to exactly 100%. Anything over 100% is the sportsbook's built-in hold. We split it proportionally to approximate a fair line - useful as a baseline, not a guaranteed truth.
What implied probability actually tells you
Implied probability is the break-even win rate a sportsbook's odds quote. It is not the book's estimate of the true probability - it is the true probability plus the margin (vig) the book takes. If a price implies 52.4% and you can't beat that win rate, the bet is -EV in the long run regardless of how often it cashes in any short sample.
Formulas this tool uses
- Negative American odds → implied probability = |odds| / (|odds| + 100)
- Positive American odds → implied probability = 100 / (odds + 100)
- Two-way hold = (implied A + implied B) − 1
- Fair (no-vig) probability = implied / (implied A + implied B)
Worked example - standard -110 / -110 spread
Both sides imply 110 / 210 ≈ 52.38%. Total = 104.76%, so the hold is 4.76%. The fair no-vig probability for each side is 52.38 / 104.76 ≈ 50% - exactly what you would expect from a perfectly balanced market with zero margin.
Worked example - uneven market (-200 / +170)
-200 implies 66.7%. +170 implies 37.0%. Total = 103.7% (hold ≈ 3.7%). Fair no-vig probabilities are 64.3% and 35.7%. If your model says the favorite is closer to 60%, the -200 price is significantly -EV even after stripping the vig.
Common questions
- Why don't the two sides of a market add up to 100%?
- Because the sportsbook prices in a margin. The amount above 100% is the theoretical hold.
- Is the no-vig probability the "true" probability?
- It is an approximation. Splitting the vig proportionally is a reasonable baseline but assumes the book's margin is distributed evenly across sides, which is not always true on uneven markets.
- How is implied probability used in expected value calculations?
- EV requires comparing your estimate of the true probability to the implied probability of the price. If your true estimate exceeds implied by more than the vig, the bet is +EV.