Vig, Juice and Overround, Explained
Three names for the same number — the guaranteed margin every sportsbook embeds in its odds. This guide unpacks exactly how that margin is built, how to measure it in 2-way and 3-way markets, how to strip it from a line, and why sharp books like Pinnacle can afford a 2% margin while soft books charge 8% or more.
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The first thing to understand about betting odds is that they are not probabilities. They are prices — prices that include a built-in commission charged by the bookmaker for offering the market. If a fair coin's true probability of heads is 50%, no sportsbook would offer you 2.00 on both sides, because then they would have zero edge. Instead they offer, say, 1.91 on each side. The implied probabilities now sum to 104.71% rather than 100%, and that 4.71% excess is the bookmaker's margin.
Americans call this vig (short for vigorish, a Yiddish-derived street-gambling term) or juice. British bookmakers call it overround. Quants call it margin. All four refer to the same quantity: the amount by which the sum of implied probabilities exceeds 100%. Understanding it is step one of any serious betting strategy, because every EV calculation starts by stripping the vig out of the line.
1. The Math of Overround
# Implied probability from decimal odds p_implied(O) = 1 / O # Overround for an N-outcome market Overround = ( sum_i (1 / O_i) ) - 1 # Vig% (same idea, as a percentage) Vig% = 100 * Overround # Margin per outcome (approximate, proportional attribution) Margin_i = (1 / O_i) * Overround / sum_j (1 / O_j) # Example: two-way market at -110 / -110 (decimal 1.909 / 1.909) sum_implied = 1/1.909 + 1/1.909 = 0.5238 + 0.5238 = 1.0476 Overround = 0.0476 (4.76%) Vig% = 4.76% # Example: -105 / -115 (decimal 1.952 / 1.870) sum_implied = 1/1.952 + 1/1.870 = 0.5123 + 0.5348 = 1.0471 Vig% = 4.71%
Notice that the vig is almost identical in the two examples above — just under 4.75%. What changed is how that margin is distributed: in a -105/-115 line, the book tilted the margin more onto the Under side (or whichever side is at -115), suggesting heavier action or perceived risk on that side. Sharp bettors read this asymmetry as a signal about the book's view.
2. Three-Way Markets (Soccer 1X2)
Soccer's three-outcome moneyline (home win / draw / away win) lets bookmakers hide larger margins inside a longer list of outcomes. A typical Premier League 1X2 market at a soft book might look like the following:
| Outcome | Decimal Odds | Implied % | No-Vig Fair % | Fair Decimal |
|---|---|---|---|---|
| Home Win | 1.85 | 54.05% | 50.36% | 1.986 |
| Draw | 3.75 | 26.67% | 24.85% | 4.024 |
| Away Win | 4.50 | 22.22% | 20.70% | 4.830 |
| Sum | — | 107.33% | 100.00% | — |
Overround = 0.5405 + 0.2667 + 0.2222 = 1.0733 Vig% = 7.33% Proportional de-vig (each implied / sum): Home win = 0.5405 / 1.0733 = 0.5036 -> 50.36% Draw = 0.2667 / 1.0733 = 0.2485 -> 24.85% Away win = 0.2222 / 1.0733 = 0.2070 -> 20.70% Sum = 1.0000 (100.00%) Fair decimal odds (no-vig): Home = 1 / 0.5036 = 1.986 Draw = 1 / 0.2485 = 4.024 Away = 1 / 0.2070 = 4.830
The same line at Pinnacle might read 1.95 / 3.95 / 4.75 for an overround closer to 2.1%. The Pinnacle fair-probability estimate is essentially the same once you de-vig, but the price the bettor receives is meaningfully better. Over hundreds of soccer bets, the 5-percentage-point vig gap between soft books and sharp books compounds into tens of thousands of dollars for a serious bettor.
3. Soft vs Sharp Book Margins
| Book | Segment | NFL Spread Vig | Soccer 1X2 Vig | Props / Futures Vig |
|---|---|---|---|---|
| Pinnacle | Sharp | 2.2% - 2.5% | 2.0% - 2.4% | 3.5% - 5.0% |
| Circa | Sharp (US) | 2.0% - 2.5% | n/a | 4.0% - 6.0% |
| BetCRIS | Sharp | 2.0% - 2.8% | 2.2% - 2.5% | 4.0% - 6.0% |
| Bookmaker.eu | Sharp-ish | 3.0% - 4.0% | 4.0% - 5.0% | 5.0% - 8.0% |
| FanDuel / DraftKings | Soft (US retail) | 4.5% - 5.2% | 6.0% - 8.0% | 8.0% - 15.0% |
| Bet365 | Soft (global) | 4.0% - 5.0% | 4.5% - 6.5% | 6.0% - 12.0% |
| Caesars / MGM | Soft (US) | 4.5% - 5.5% | 6.5% - 8.5% | 9.0% - 18.0% |
The spread between Pinnacle and a typical US retail book is roughly 2-3 percentage points on spreads and 4-6 percentage points on soccer and props. If you bet $100 per wager at -110 / -110, you pay about $4.55 in vig per bet; at -115 / -115 you pay about $6.98. That extra $2.43 per wager is a pure expected-value loss, independent of whether the bet wins. Across 1,000 bets per year that is $2,430 of avoidable cost.
4. Why Pinnacle Can Charge 2%
Pinnacle welcomes sharp action and uses it as a pricing signal. Sharp bettors refine the line, Pinnacle adjusts, the line gets closer to truth, lower vig still produces profit because volume is enormous.
Soft books subsidise their marketing and promos from their vig. Pinnacle runs a stripped-down operation: no bonuses, no loyalty points, no promotions. The savings flow back into tighter prices.
Retail US books aggressively limit or ban sharp bettors. Their customer base is structurally losing, so they can charge 6-8% without losing significant volume. Limiting sharps protects that model.
Soft books hide the worst vig in prop markets and parlays where recreational bettors concentrate. A 2-way prop at -135 / -105 is 9% vig — advertised as a "fun bet" but in reality one of the worst prices on the board.
5. De-Vig Methods Compared
# Proportional (multiplicative) de-vig — default choice
p_fair(i) = p_implied(i) / sum_j p_implied(j)
# Example: NBA ML Lakers 1.72 / Celtics 2.30
p_imp = [0.5814, 0.4348] sum = 1.0162 vig = 1.62%
p_fair = [0.5814/1.0162, 0.4348/1.0162]
= [0.5721, 0.4279]
fair_decimal = [1.748, 2.337]
# Logarithmic (Shin) de-vig — favors favorites slightly
# Solve for z in: sum_i sqrt(z^2 + 4*(1-z)*p_imp(i)^2 / sum_j p_imp(j)) = 2
# Then p_fair(i) proportional to sqrt(z^2 + 4*(1-z)*p_imp(i)^2/sum) - z
# On the same NBA ML:
Shin-adjusted p_fair = [0.5748, 0.4252] (slightly more on favorite)
fair_decimal = [1.740, 2.352]
# Worell / basic-margin-model — assumes vig proportional to price
# Less common, slightly worse out-of-sample fit than proportional
# When proportional de-vig is fine
- Two-way markets with vig <= 5%
- Markets where both sides have similar liquidity
- Most standard 1X2 soccer markets
# When Shin / logarithmic is better
- Heavy-favorite moneylines (e.g. soccer cup ties, lopsided NFL games)
- Three-outcome markets where the favorite is very short
- When empirical favorite-longshot bias matters to your betFor the vast majority of retail bettors, proportional de-vig is accurate within 0.3 percentage points of the logarithmic method and is dramatically easier to compute in a spreadsheet. Use proportional by default. Switch to Shin de-vig only when you are pricing heavy favorites (decimal odds below 1.40) or when your model disagrees materially with the proportional result.
6. How Vig Compounds on Parlays
One single -110 bet costs roughly 4.55% in vig. A four-leg parlay of -110 bets does not cost 4.55% — it compounds. The true compounded edge is 1 − (0.9545)^4 = 16.97%. The book takes roughly 17 cents of every expected dollar on a four-leg parlay even though each individual leg appears to be a fair 4.5% vig. This is why parlay math is one of the ugliest EV situations for recreational bettors.
7. Frequently Asked Questions
What is vig in sports betting?
Vig, juice, or overround is the commission embedded in the odds. It is measured as the excess over 100% when you sum all outcomes' implied probabilities. At -110 / -110 the sum is 104.76%, so the vig is 4.76%.
How do I calculate bookmaker vig?
Convert each decimal odds to implied probability (1/odds), sum them, subtract 1, multiply by 100. For US odds, convert to decimal first (positive American: 1 + odds/100; negative: 1 + 100/|odds|).
Is vig always split equally between both sides?
No. A -105/-115 line has the same total vig (~4.71%) as -110/-110 but loads more of it onto the -115 side. Books tilt the margin to balance action or to reflect their view of where the true probability sits.
Why does 3-way vig look higher than 2-way vig?
Three-outcome markets give the book an extra slot to hide margin in. A 3-way market at 7% overround and a 2-way market at 4.7% overround can correspond to similar per-outcome mispricing; the comparison is misleading unless normalized per outcome.
How does vig interact with CLV and EV?
EV is computed against the no-vig fair probability. CLV is computed against the no-vig closing line. Always strip the vig before calculating either metric — comparing your price to a raw-vig price understates your true edge or disadvantage.
Quantify your book's take with the margin calculator, then compute fair prices using no-vig fair odds, and convert American / decimal with the odds converter.
Responsible gambling notice. This article is educational. Knowing how vig works does not guarantee profit — every wager carries financial risk. Stake only what you can afford to lose. For support with problem gambling visit BeGambleAware.org or call 1-800-GAMBLER (US). Must be of legal betting age in your jurisdiction.