▌ Calculator · no-vig odds · updated 2026-05-08
Vigorish (vig) is the bookmaker's built-in edge. Every odds line includes commission — both sides of a moneyline at -110/-110 imply 104.76% probability, not 100%. This calculator removes it to find the "fair line" — the true probability each outcome should carry. Convert American, decimal, or fractional odds for any 2-way or 3-way market in one click.
Matched bettors use no-vig calculations to find arbitrage opportunities — opposite lines at different books where both sides offer value. Even casual bettors benefit from seeing what the bookmaker actually believes, stripped of commission. Once you have fair odds, use our hedge calculator to lock in profit.
▌ Inputs
Market type
Moneyline, spread, total. Two mutually exclusive outcomes.
▌ Fair odds (no vig)
Bookmaker's edge (vig)
0.0%
Side A fair
2.00
50.0%
Implied prob
50.0%
Side B fair
2.00
50.0%
Implied prob
50.0%
Overround (prob sum) · 100.00%
The vig is how much the odds "overround" 100%. Remove it to find fair value.
▌ Derivation · probability math
Odds are a bet's payout ratio. Decimal odds of 2.50
means a $1 bet pays $2.50
if it wins. The implied probability is 1 / odds,
or in this case 1 / 2.50 = 40%.
For two mutually exclusive outcomes, the sum of implied probabilities should equal 100%.
But bookmakers add a margin. For example, two sides at -110
American (2.00 decimal each) imply 50% + 50% = 100%, which is fair. But at
-110 on both sides, the actual line is slightly short:
100 / 110 ≈ 90.9% payout per side, so true decimal is
1.909. Implied probability ≈ 52.38% per side, summing to
104.76%. The extra 4.76% is the vig.
Let A and B
be decimal odds for two outcomes:
p_A = 1 / A p_B = 1 / B overround = p_A + p_B (always >100%)
To find fair odds, rescale each probability down by the overround:
fair_p_A = p_A / overround fair_A = 1 / fair_p_A
The vig percentage is (overround − 1) × 100. For
the -110/-110 example: (1.0476 − 1) × 100 = 4.76%.
Same logic, but with three outcomes (home, draw, away). The overround is the sum of all three implied probabilities. Each fair probability is scaled down by this sum:
fair_p_outcome = p_outcome / (p_home + p_draw + p_away)
Convert back to decimal odds and you have the fair 3-way line with vig removed.
▌ Worked example
Example: A moneyline at -110 / -110 (American).
−110 American → 100 / 110 + 1 = 1.909
decimal
Side A: 1 / 1.909 ≈ 52.38%
Side B: 1 / 1.909 ≈ 52.38%
Overround: 52.38% + 52.38% = 104.76%
Fair prob Side A: 52.38% / 104.76% = 50%
Fair prob Side B: 52.38% / 104.76% = 50%
Fair decimal: 1 / 0.50 = 2.0 (even money)
(1.0476 − 1) × 100 = 4.76%
The bookmaker's edge is 4.76% on a -110 / -110 line.
In this case, the -110/-110 line is exactly fair (50/50 odds). But most lines have different odds on each side. A -120/+100 line tips the edge toward one side. Run it through the calculator to see the fair probabilities and vig.
▌ Applications
Use the calculator on both sides of the same outcome at different books. If both sides show mathematical edge (fair odds more favorable than the actual line), an arbitrage exists. Lock in guaranteed profit by betting both sides.
Fair odds show where the bookmaker thinks value sits. If you disagree with fair odds, use that gap to size a hedge that isolates your edge. Hedge to the fair line if you want neutral downside; hedge less if you have strong conviction.
Compare fair odds to your own probability estimates. If fair is 55% but you estimate 60%, that 5% gap is your edge. Use Kelly criterion (see the methodology page) to convert edge into optimal bet size.
See exactly how much commission the book is taking. A 6% vig is lower-cost than 10%. Comparison shop for lines with lower vig on the outcomes you trade most.
/ — methodology
The methodology page covers Kelly criterion (Kelly 1956), hedge math, implied probability vs implied odds, UK bookmaker bonus rules, and per-state US tax math — every formula cited to a primary source.