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The house always wins because they artificially inflate probabilities. Remove the Vig from any two-way market to discover the true, mathematically fair betting line.
Last updated: February 24, 2026
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American odds (e.g. -110)
American odds (e.g. +100)
Side 1
+100
50.0% implied
Side 2
+100
50.0% implied
Total Implied Target
104.76%
Bookmaker's Margin
4.76%
A fair coin flip has a 50% chance of Heads and a 50% chance of Tails. The probabilities add up to precisely 100%. A sportsbook offers -110 on both sides. Evaluated mathematically, -110 implies a 52.4% probability. 52.4 + 52.4 = 104.8%. This excess 4.8% is called the overround.
To find the true probability, we must scale those inflated, vig-heavy probabilities back down so they equal 100%. If Team A's vig-inflated probability is 60% and Team B's is 45% (Total 105%), dividing 60 by 105 gives Team A a mathematically true win probability of 57.14%.
Why do this? You use the No-Vig calculator on the sharpest sportsbook in the world to find what the "True Line" is. If the sharp book says the True Line is -130 (56.5% chance), but your local sportsbook is offering -115 (53.5% implied), you have a mathematical edge over your local book.
No-vig odds (also called fair odds or true odds) are betting prices after removing the bookmaker margin. Sportsbooks build in vig so the displayed odds do not represent pure probability. A no-vig calculator strips out that edge so you can evaluate a market on neutral math.
This matters because expected value (EV) depends on true probability, not posted probability. If you compare a soft book's line to a no-vig baseline from a sharp market, you can identify potentially profitable mispriced opportunities.
Bettors and traders use no-vig pricing for market making, line shopping, arbitrage screening, bankroll modeling, and validating whether a wager is genuinely +EV over large sample sizes.
For negative American odds: implied probability = |odds| / (|odds| + 100)
For positive American odds: implied probability = 100 / (odds + 100)
Overround: p1 + p2
No-vig probability (side A): p1 / (p1 + p2)
No-vig probability (side B): p2 / (p1 + p2)
Where p1 and p2 are the raw implied probabilities from each side. Normalization forces both sides to sum to 100%, revealing the true fair market probabilities without sportsbook juice.
Raw implied: 52.38% / 52.38%
Overround: 104.76%
No-vig: 50.00% / 50.00%
True fair line is roughly +100 / +100.
Raw implied: 58.33% / 45.45%
Overround: 103.78%
No-vig: 56.21% / 43.79%
Fair price is softer than the posted favorite line.
Raw implied: 64.29% / 39.22%
Overround: 103.50%
No-vig: 62.11% / 37.89%
Even small edges matter for long-term ROI.
The table below compares typical market pricing, overround, and no-vig conversion outcomes for common two-way lines.
| Posted Market | Implied Total | Overround (Vig) | No-Vig Probability Split | Fair-Odds Insight |
|---|---|---|---|---|
| -110 / -110 | 104.76% | 4.76% | 50.00% / 50.00% | True coin-flip market |
| -120 / +100 | 104.55% | 4.55% | 54.55% / 45.45% | Moderate favorite edge |
| -140 / +120 | 103.78% | 3.78% | 56.21% / 43.79% | Lower hold, sharper pricing |
| -180 / +155 | 103.50% | 3.50% | 62.11% / 37.89% | Heavy favorite market |
Use fair odds as a benchmark across sportsbooks. If one operator offers a better price than true no-vig value, that line may carry positive expected value.
Quantify edge before staking capital. Combining no-vig pricing with bankroll strategy helps reduce emotional betting and improves long-run decision quality.
Stop betting blindly. Share this fair-odds calculator with your trading syndicate or betting group to ensure you're only taking mathematically sound positions.
Suggested hashtags: #SportsBetting #ExpectedValue #PlusEV #MatchedBetting #MathFinance