Every sportsbook price has a small tax baked in. It doesn’t appear on your bet slip or in the terms, and most bettors never calculate it. It’s the bookmaker’s margin, also called the vig, the juice or the overround, and it decides what sports betting costs you far more than any welcome bonus does. The good news: you can calculate it on any market in about thirty seconds with nothing but the odds. Here’s the formula, worked examples, what regulators report books actually keep, and how to use it.
- Overround = the implied probabilities of every outcome, added up. Anything above 100% is the bookmaker edge.
- Margin = 1 - 1 / overround. A -110 / -110 market works out to 4.55%.
- Hold is what books really kept: 7.69% on sports in Nevada over 12 months to July 2026.
- Parlays compound it: four -110 legs carry about 17% built-in edge.
Where the margin comes from
Picture a fair coin. A fair price on heads is 2.00, and on tails 2.00. Bet C$100 on each side, and whichever wins, you get C$200 back. Nobody makes money.
Now a sportsbook prices the same coin at 1.91 on each side (that’s -110 in American odds). Bet C$100 on each side and you get C$191 back. The book keeps C$9 of your C$200, or 4.55%. That’s the margin: shorter-than-fair odds on every outcome, so the book earns no matter which side wins if the money is balanced.
Real games aren’t coin flips, but the principle holds. Odds that would be fair are shaved on every outcome, and the shaving shows up when you add up the implied probabilities.
🧮 The formula, step by step
Step 1: convert each price to an implied probability. Implied probability = 1 / decimal odds. (Our odds guide covers American and fractional, and the odds converter does it for you.)
Step 2: add them up. The total is the overround. A fair market adds to exactly 100%.
Step 3: turn it into a margin. Margin = 1 - 1 / overround. That’s the share of all stakes the book keeps if it balances its book. The theoretical payout to bettors is 1 / overround.
Some sources quote the margin as simply overround minus 100%. That number is slightly higher (4.76% instead of 4.55% on a -110 market), so always say which one you mean. We use 1 - 1 / overround throughout.
Worked example, the standard two-way line: 1 / 1.909 = 52.38% on each side. Overround: 104.76%. Payout: 1 / 1.0476 = 95.45%. Margin: 4.55%.
A moneyline with uneven prices
Most games aren’t priced the same on both sides, and the method doesn’t change. Worked example, illustrative odds: a hockey moneyline with the favourite at -150 and the underdog at +130.
- -150 implies 150 / 250 = 60.00%.
- +130 implies 100 / 230 = 43.48%.
- Overround: 103.48%. Margin: 1 - 1 / 1.0348 = 3.36%.
That’s a tighter price than the -110 / -110 line, even though neither side looks “cheap”. The point is to calculate, not eyeball. A big favourite at short odds can carry more margin than the underdog, or less, and the only way to know is to convert both sides and add them up.
The break-even win rate
Margin also tells you how often you have to be right just to stay level. At -110, you stake C$110 to win C$100, so you need to win 110 out of every 210 bets, or 52.38%, to break even. That’s the implied probability of the price, and it’s no coincidence. Win 50% of -110 bets, which is what a coin flip would give you, and you lose about 4.55% of everything staked over time.
Worked example, illustrative: 100 bets of C$10 at -110, winning exactly half. Fifty winners return C$19.09 each, C$954.50 in total, against C$1,000 staked. The C$45.50 gap is the margin at work, 4.55% of turnover.
Margin on four kinds of market
The more outcomes a market has, the more room there is to shave each one. Here’s the same calculation run on four markets.
| Market | Odds | Overround | Payout | Margin |
|---|---|---|---|---|
| Two-way line at -110 / -110 (puck line, spread, total) | 1.909 / 1.909 | 104.76% | 95.45% | 4.55% |
| Soccer 1X2, odds used by Hegarty and Whelan | 1.90 / 4.76 / 3.17 | 105.19% | 95.07% | 4.93% |
| NHL 60-minute three-way (illustrative) | 2.20 / 4.00 / 2.75 | 106.82% | 93.62% | 6.38% |
| Four-runner futures market (illustrative) | 3.00 / 3.50 / 4.00 / 4.50 | 109.13% | 91.64% | 8.36% |
Computed by BonusMadness; soccer odds from Hegarty and Whelan’s CEPR VoxEU column, other odds illustrative.
🧮 Margin by market type
| Two-way -110 / -110 | 4.55% |
|---|---|
| Soccer 1X2 | 4.93% |
| NHL 60-min three-way (illustrative) | 6.38% |
| Four-runner future (illustrative) | 8.36% |
We looked for a credible published table of typical margins by market type (moneyline vs props vs futures vs live) and didn’t find one from a regulator or academic source, so the table above uses worked examples rather than averages. One academic finding does help: in a study of 84,230 European soccer matches from 2011 to 2022, Hegarty and Whelan found that Asian handicap bets have lower margins than 1X2 bets, and that 1X2 longshots lose more per dollar than favourites. That’s the favourite-longshot bias, and it’s why long odds on a three-way market often carry the worst value. Our soccer betting guide covers Asian handicap in detail.
Margin vs hold: what books really keep
Margin is what the prices promise the book. Hold is what it actually kept: win divided by amount wagered, as regulators report it. Hold differs because results swing, parlays carry stacked margins, and the money rarely lands evenly on both sides.
Nevada sportsbook hold by sport, 12 months to July 2026
| Basketball | 6.78% |
|---|---|
| Baseball | 6.85% |
| Football | 7.29% |
| All sports | 7.69% |
| Hockey | 8.73% |
| Other | 9.91% |
| Parlay cards | 30.07% |
Nevada is the longest-running regulated sports market with public data by sport, and its books held 7.69% overall. Hockey ran highest of the major sports at 8.73%. Parlay cards, the fixed paper product, held 30.07%.
Canada has its own data point. In fiscal 2024-25, Ontario’s regulated market took C$11.4 billion in betting wagers and kept C$724 million in betting revenue, according to iGaming Ontario. That’s a computed hold of 6.35%. The same release puts casino at C$69.6 billion wagered and C$2.4 billion kept, a 3.45% hold. On those numbers, each dollar bet on sports in Ontario cost bettors nearly twice what a dollar in the casino did.
Why margin matters more than the bonus
A welcome bonus is a one-off. The margin applies to every bet you ever place. Here’s the comparison, worked with illustrative numbers.
| Scenario | Bets placed | Margin | Average cost |
|---|---|---|---|
| Clearing a C$100 bonus at 5x on singles | C$500 | 4.55% | C$22.75 |
| A season of singles on -110 two-way markets | C$5,000 | 4.55% | C$227.50 |
| The same season on three-way markets | C$5,000 | 6.38% | C$319.00 |
Computed by BonusMadness; average cost = bets placed x margin. Illustrative.
The gap between the two seasons is C$91.50, close to the whole value of a C$100 bonus. Shave a point or two off the margin you pay, by choosing markets and books with tighter prices, and the saving repeats every season. A bonus pays once. Our sports bonuses guide runs the bonus side of the maths in full.
How margin compounds in parlays
In a parlay, the odds of each leg multiply, and so does each leg’s payout share. Four legs at -110 each return 95.45% x 95.45% x 95.45% x 95.45% = 83.02% on average, a built-in edge of about 17%. Ten legs: about 37%. Our parlay guide has the full table, and the parlay calculator shows the combined odds for any slip.
Using margin in practice
- Check both sides. Add the implied probabilities of a two-way market. Near 104.8% is standard; higher means you’re paying more.
- Prefer two-way markets when you have a view. A spread or total usually carries less margin than a three-way result or a long futures list.
- Compare books before betting. The same game can carry different prices at different books. Our sportsbook list and guide to choosing a sportsbook put pricing alongside licence and payouts.
- Count parlay legs. Each one adds margin.
🍁 Before you bet
Knowing the margin tells you what betting costs, not what it pays. No market is priced in your favour by default, and betting is entertainment, not income. The Canada sports betting guide covers who runs betting in each province. Everything we cover is for players aged 19 or over outside Ontario and Alberta. Set a monthly budget before your first bet, and see our responsible gambling page for every provincial helpline.
FAQ
What is the vig or juice in sports betting?
It's the bookmaker's built-in margin: the share of the money bet on a market that the book expects to keep. It shows up as odds slightly shorter than fair. On a two-way market priced -110 on both sides, the margin is about 4.55%.
How do I calculate a bookmaker's margin?
Convert each outcome's decimal odds to an implied probability (1 divided by the odds) and add them up. That total is the overround. The margin is 1 minus 1 divided by the overround. For -110 / -110: 52.38% + 52.38% = 104.76%, and 1 - 1/1.0476 = 4.55%.
What is the difference between margin and hold?
Margin is the edge built into the prices. Hold is what books actually kept from the money wagered over a period, as reported by regulators. Hold runs higher than a clean two-way margin because of parlays, props and where the money lands. Nevada books held 7.69% on sports over the 12 months to July 2026.
Which bets have the lowest margin?
Two-way main markets such as spreads and totals at -110 sit around 4.55%. Three-way markets and futures carry more because the margin is spread over more outcomes. In soccer research, Asian handicap bets showed lower margins than 1X2 bets. Parlays compound the margin of every leg.
Does a lower margin mean I will win?
No. A lower margin means each bet costs less on average, so your money lasts longer for the same betting. Every bet still carries an edge for the book. Margin tells you the price, not the result.
