The Vig Math: Why -110 Is a 52.38% Break-Even, and What to Do About It

Every -110 bet you place costs you 4.76% in margin. Most bettors know that number in isolation. Few understand what it compounds into across a full season, or why the 9.3% realized hold US sportsbooks posted in 2024 reveals a cost far larger than the posted price.

This is the complete vig explainer: the formula, the break-even table, why different markets carry radically different margins, how to strip the vig out to find the true price, and what to do about all of it.

The Formula

Standard NFL spread or totals pricing: Team A −110, Team B −110.

The implied probability for each side comes from the American odds directly.

Both outcomes together sum to 104.76%. The extra 4.76% is the vigorish. A fair, zero-margin market sums exactly to 100%.

The break-even calculation follows directly. At −110, you risk $110 to win $100. The rate you need to win to break even:

Win 52.38% of your −110 bets and you break exactly even. Win less, you lose money. Win more, you profit.

The sportsbook does not need to know who will win. It collects from both sides and pays out at prices that do not sum to fair value. The book's edge is structural, not predictive.

Your Break-Even Rate Changes With Every Nickel of Juice

The table below covers the most common price points. All figures use transparent arithmetic. Break-even formula: X/(X+100) at odds −X. Market vig for a symmetric −X/−X market: (X−100)/(X+100). Expected loss per $1,000 at risk assumes 50% true probability, using: 0.5 × (100,000/X) − 500.

The gap between −105 and −110 is 1.16 percentage points of required win rate. Across a 500-bet season where you wager $110 per game, that difference costs exactly $500 in expected value. From nothing but the posted price, with no change in your handicapping quality.

At −110, your expected loss per bet (at 50% true probability) is $5. At −108, it drops to $4. Line shopping for two cents of juice on every bet saves $1 per wager. That sounds small. Across 500 bets, it is $500 in expected value before you have predicted a single game correctly.

Where Sportsbooks Actually Hide the Margin

Game lines, spreads and totals, are the most competitive markets at any US sportsbook. Sharp bettor pressure and market liquidity force pricing close to fair value. The −110/−110 standard is where books compete hardest against each other and against sharp money.

Move off the game lines and the margin expands quickly.

A bettor who confines action to game lines at a sharp book faces a structural disadvantage roughly 50% smaller than one betting player props at a recreational book. The game is the same. The price difference is not.

Player prop markets carry higher vig for a reason the book's pricing desk understands well: less sharp action, noisier models, and thinner liquidity all reduce competitive pressure on the book. The book prices its uncertainty into the margin and charges you for it.

Removing the Vig: The Four Methods

Sportsbooks rarely post perfectly balanced −110/−110 lines. When one side gets more action, the book shades the price. A −115/−105 line tells you the book wants fewer bets on side A, but it does not tell you the fair probability the book is implying. To find that, you strip out the vig.

The worked example below uses a −115/−105 line. The first step for all four methods is identical: convert both odds to implied probabilities.

Multiplicative method

Divide each side's implied probability by the total. The vig is distributed proportionally. The side with higher implied probability absorbs more of it.

Additive method

Subtract half the total vig from each side equally, regardless of which side carries more weight.

For a symmetric −110/−110 market, both methods produce the same result: 50% fair probability for each side. The methods diverge on unbalanced lines like this −115/−105 example. Multiplicative gives −104/+104. Additive gives −105/+105. The one-point spread between the methods grows on lines with bigger imbalances.

The multiplicative method is the standard default for two-way markets. It distributes vig in proportion to implied size and is the method most commonly used by professional tools.

Power and Shin methods

The power method raises implied probabilities to a constant power that accounts for the favorite-longshot bias. The Shin method uses an iterative algorithm to correct specifically for insider trading effects that inflate longshot prices. Both are more accurate on large favorites (−200 or heavier) or multi-way markets like outrights. For standard two-way spread and totals, multiplicative is sufficient.

The Devig Calculator

Why the Overround Understates Your True Cost

The 4.76% vig on a −110/−110 spread is the posted margin on that specific market. The actual cost to the average bettor runs higher. A 2025 paper in Applied Economics by Hegarty and Whelan quantified why.

Their finding: when bookmakers charge higher profit margins on lower-probability outcomes, the pattern called the favorite-longshot bias, the standard overround formula understates the average expected loss rate across all bets a bettor places. The paper covered 41 bookmakers across 11 European soccer and tennis leagues. The overround on any given market tells you the margin on that market. It does not tell you your average effective margin across a portfolio of bets that includes favorites, underdogs, and mixed-line props.

The mechanism: books charge a heavier margin on longshots than on favorites. A bettor who places action on both sides of the board pays a higher blended effective vig than the posted overround on any individual market implies. Bettors who concentrate money on favorites compound the problem because public-facing books shade favorite prices against the expected public action, increasing the implied overround on those bets above the posted market figure.

The single-market overround figure does not capture your effective portfolio margin, especially when your action clusters on favorites, which is where most recreational bettors concentrate. The Whelan and Hegarty finding provides academic backing for what practitioners have long observed.

What $149.8 Billion in Handle Tells You

In 2024, US sportsbooks took $149.8 billion in handle and retained $13.71 billion in revenue, per the American Gaming Association and confirmed by ESPN reporting. The realized hold rate: 9.3%.

The three drivers of the gap between posted 4.76% and realized 9.3%:

1. Prop market exposure. Player props at 6-10% vig represent a large and growing share of total handle. Every bet you place on a prop at −115 or worse contributes to a higher effective margin than the spread market alone implies.

2. Parlay and same-game parlay construction. A two-team parlay at −110/−110 carries a theoretical hold above 10%, depending on correlation assumptions. SGPs push higher. The portion of handle in parlay markets, now the primary revenue driver for most US retail books, comes with margins well above the single-game line standard.

3. Favorite concentration and moneyline pricing. Public bettors concentrate money on favorites. On lopsided moneylines, the book prices the vig into both sides but faces one-sided action. The realized hold on money-heavy favorites often exceeds the posted overround because the book has already shaded the line against public betting flow.

The 9.3% figure is not a sportsbook confession. It is a reflection of what bettors actually bet. If you confine action to sharp-priced game lines and avoid prop parlays, your effective margin is much closer to the posted vig. If you mirror the average bettor, you pay something closer to 9.3 cents per dollar wagered.

Three Steps That Reduce Your Effective Vig Today

1. Line shop on every single bet

The break-even rate at −108 is 51.92%. At −110, it is 52.38%. That 0.46 percentage point difference applies across every bet you place for the rest of your betting life. At 500 bets per season, $110 per bet, the expected value difference between always getting −108 versus always getting −110 is $500 per year. Before you have predicted a single game correctly.

The gap between the best and worst posted price on the same NFL spread game regularly hits 5 cents. DraftKings, FanDuel, BetMGM, and Caesars post different prices on the same market for the same game. Using the best available number closes that gap entirely at zero cost.

2. Devig before you bet props

A raw −115 price on a player prop tells you nothing about whether you have an edge. The devigged fair probability tells you what probability the book is implying at fair value. If the book implies 51% and your own estimate is 55%, you have a 4% edge. If you have no independent estimate, you are paying 6-10% vig to guess.

Use the calculator above on any prop before placing the bet. Enter both sides. Read the fair probability. Compare it to what you think the real probability is. If the gap is not at least 3-5 percentage points in your favor, the bet does not clear the vig bar.

3. Treat market type as a vig decision before it is a pick decision

A player prop at −120/+100 carries a total implied of 54.5% + 50.0% = 104.5%. An NFL spread at −110/−110 carries 104.76%. On the surface they look similar. The prop's vig is lower in this case. But props at those prices are rare. Most prop markets come in at −115/−105 or worse, carrying 6-7% vig.

Futures are the worst. A 15% vig on an NFL division winner means you need to outperform the implied probability by 15 percentage points. On a four-team division market, the fair favorite might be implied at 35%. The posted price implies 40%. You need to hold a genuine edge above the fair 35% probability, not merely be closer to the shaded 40% posted price.

The sharpest bettors do not pick markets based on what feels interesting. They pick markets based on where their information advantage exceeds the vig cost. On game lines at 4.76% vig, a 3% edge produces positive expected value. On a futures market at 15% vig, a 3% edge loses money. The market type choice is a mathematical decision before it is a picks decision.

The CLV Connection

Closing line value, the metric that measures whether the line moved in your direction after you bet, requires devigging both your entry price and the closing price to produce a meaningful comparison. An article in this series, Closing Line Value Explained, covers the full no-vig CLV formula.

The vig math and CLV connect directly. A positive no-vig CLV across a meaningful sample is evidence that you are pricing markets better than the book's closing line. That is the closest thing to a verifiable proof of edge available to a sports bettor. The formula only works if you strip the vig correctly. The multiplicative devig in this article and the calculator above are the prerequisite math.

Understanding the vig does not guarantee winning bets. But betting without it guarantees paying more than you need to on every wager you place.