How Bookmaker Margins Work

What a bookmaker margin actually is

Fair odds reflect the true probability of an outcome. If a tennis match between two evenly matched players were priced fairly, both sides would be 2.00 in decimal odds — each implying a 50% chance, totalling exactly 100%.

But sportsbooks don't offer fair odds. They shorten both prices slightly, say to 1.91 and 1.91. Convert those back to implied probability and each is 52.4%, totalling 104.8%. That extra 4.8% is the margin. It's the theoretical edge the book holds if it balances its liabilities across all bettors.

The margin is not a fee you see on a receipt. It's invisible, embedded in every price, and it applies whether you win or lose. Understanding it is the single most useful skill for comparing where your money goes furthest.

How to calculate margin from any odds line

The maths is simple and works for any market. Two steps:

• Convert each decimal price to implied probability: 1 ÷ odds.
• Add the probabilities together, then subtract 100%.

For a two-way market (like a moneyline with no draw, or over/under):

Margin = (1 ÷ odds A) + (1 ÷ odds B) − 1

Example: an NHL puck-line priced 1.87 / 2.05. - 1 ÷ 1.87 = 0.5348 (53.48%) - 1 ÷ 2.05 = 0.4878 (48.78%) - Total = 102.26% → margin = 2.26%

For three-way markets (football 1X2 with home/draw/away), add all three implied probabilities and subtract 100%. The more outcomes a market has, the more room a book has to hide margin — which is why long-list markets like first goalscorer or outright winners tend to carry far higher overrounds than a simple two-way line.

A worked example: what margin costs you on a real stake

Say you want to back the same NHL favourite at two operators. Book A prices it 1.87; Book B prices it 1.95. Both books think the true chance is roughly the same — the difference is margin.

Stake $100 on a winner: - Book A at 1.87 returns $187 → $87 profit. - Book B at 1.95 returns $195 → $95 profit.

That's $8 more on a single winning bet, purely from the price. Over a season of 200 similar bets, the same 0.08 difference in average odds compounds into hundreds of dollars — with no change in your skill or luck.

Now scale it with margin data. On our sampled markets Pinnacle averaged a 3.12% margin while LeoVegas averaged 6.86%. On a market where the fair price would be 2.00, a 3.12% margin might leave you around 1.94, whereas a 6.86% margin might leave you nearer 1.87. Same outcome, same stake — noticeably different payout. Margin is the quiet tax on every ticket, so shopping the line matters more than any promotion.

How margin varies by sport and market

Margin is never one number for a whole sportsbook. It shifts by sport, by market type, and by how much money is expected on an event.

• Big, liquid two-way lines — an NBA moneyline, an NHL puck-line, an MLB run-line, a UFC main-event two-way market — usually carry the tightest margins because operators compete hard on marquee prices.
• Three-way football markets (Champions League, Serie A, Ligue 1 1X2) sit a bit higher because there are three outcomes to load.
• Player props, same game parlays and long outright lists (World Cup winner, NFL futures) carry the fattest margins. Every added selection is another place to build in overround.

This is why an operator can look sharp on hockey moneylines and expensive on a 20-runner outright. When you compare books, compare the specific market you actually bet — not a headline average.

How Ontario sportsbooks compare on margin and price

Where we have sampled odds data, two figures matter: average margin (lower is better for you) and best-price share — how often that book posted the top price in the sample (higher means it more often beat rivals).

Sharp-priced end of our sample: - Pinnacle — avg margin 3.12%, best-price share 53.4% (221 markets sampled). The lowest margin we tracked, matching its 9.4 odds rating. - FanDuel — avg margin 4.06%, best-price share 23.5% (306 sampled). - DraftKings — avg margin 4.21%, best-price share 54.5% (898 sampled) — the widest sample and frequently top of the market. - BetMGM — avg margin 4.69%, best-price share 14.6% (240 sampled). - Caesars Sportsbook — avg margin 5.35%, best-price share 36.7% (784 sampled).

Middle and higher-margin end: - Unibet — avg margin 5.74% (201 sampled). - Betway — avg margin 6.09%, best-price share 12.0% (191 sampled). - BetRivers — avg margin 6.28% (280 sampled). - 888sport — avg margin 6.63% (251 sampled). - LeoVegas — avg margin 6.86%, best-price share 6.0% (167 sampled) — the highest margin in our sample.

One caveat: sample sizes differ a lot (167 to 898 markets), and margins move by sport and market, so treat these as directional. bet365, Betano and several others in our list don't have sampled odds metrics here, so we can't quote a margin figure for them — for those, the ratings shown (bet365 8.8 on odds, Betano 8.2) reflect broader assessment, not a measured overround.

All operators above are listed as licensed under iGaming Ontario. That governs Ontario only — see the note below on why that matters across Canada.

Best-price share vs average margin: read both

Low average margin and high best-price share don't always travel together. Pinnacle combines both (3.12% margin, 53.4% best-price share), which is unusual — it's a low-frills, price-first book with fewer extras (no Bet Builder, limited features).

DraftKings shows the opposite trade-off in a good way: a 54.5% best-price share across a huge 898-market sample means it very often posts the top price, even though its average margin (4.21%) isn't the outright lowest. If you line-shop actively, best-price share tells you how often a book will actually be your pick when you compare two or three sites side by side.

A book like LeoVegas (6.0% best-price share) rarely wins the price comparison — you'd choose it for its app or payments experience, not for beating the line.

How to beat the margin in practice

You can't remove margin, but you can pay less of it:

• Hold accounts at two or three books and take the best price on each bet. Even a 0.05 difference in odds adds up over a season.
• Favour tight two-way markets over long prop and outright lists where margin balloons.
• Compare the exact market, not a headline rating — use our odds and comparison pages to check the current line.
• Weigh margin against everything else. A book with a slightly higher margin but Interac withdrawals in 0–24h, a strong app and reliable support may still be the right home base; use a sharper-priced book for shopping specific lines.

Editorial take: for pure price, our data points to Pinnacle, DraftKings and FanDuel. For a balance of competitive pricing plus features like Cash Out, Same Game Parlay and Live Streaming, DraftKings and FanDuel score well across the board. Choose a low-margin specialist for line value; avoid leaning on a high-margin book as your only account if payout per bet is your priority.