Fair odds · NetArbs guide
How to remove sportsbook vig from odds
A sportsbook price includes a margin. Converting each side to an implied probability and then normalizing the pair gives a simple estimate of the market’s fair probability. It is a comparison tool, not a prediction of the result.
Convert the prices first
For negative American odds −A, implied probability is A ÷ (A + 100). For positive odds +B, it is 100 ÷ (B + 100). Convert every mutually exclusive outcome in the market before removing margin. A two-way moneyline needs both sides; a three-way soccer result needs home, draw and away.
Do not normalize an over price against an under price from a different player, stat, line or settlement rule. The outcomes must partition the same event.
Normalize, then compare
Divide each implied probability by the sum of all outcomes’ implied probabilities. The resulting probabilities add to 100%. Convert the fair probability back to odds if you want a price to compare with another book.
A different book offering +110 on a genuinely 50% outcome has expected profit of $5 per $100 staked before other costs: a win earns $110 and a loss costs $100. The estimate only holds if the 50% input is sound and the price is still available.
Where the shortcut can fail
Simple proportional normalization assumes the margin is spread across outcomes in proportion to their implied probabilities. In lopsided markets that assumption can be poor. Sparse markets, stale quotes and different rules can be more important errors than the vig formula itself.
NetArbs compares matching lines across multiple books and exposes the market context in the odds board. Treat the fair price as an estimate and inspect the underlying quotes before acting.
See the method in NetArbs
Use the live tool to inspect the current prices and their sources. Quotes and payouts can change after this example was written.