How Bookmaker Margins Work

What a margin actually is

Every price a sportsbook posts carries an implied probability. In decimal odds, implied probability = 1 ÷ odds. A fair market for all outcomes would sum to exactly 1.00 (100%). A real market sums to more than that, and the surplus is the margin.

Think of it as the sportsbook's asking price for taking your action. It's not a fee you pay separately — it's priced silently into every line. You never get a receipt for it, which is exactly why it's worth understanding. Two books can offer the same NBA game, the same teams, the same market, and quietly charge you very different amounts to bet it.

The worked example: calculating margin from the odds

Take a two-way market — say an ATP Tour match with no draw. One book prices it:

• Player A: 1.90 decimal (-111 American)
• Player B: 1.90 decimal (-111 American)

Implied probabilities: - Player A: 1 ÷ 1.90 = 0.5263 (52.63%) - Player B: 1 ÷ 1.90 = 0.5263 (52.63%) - Total book = 105.26%

Margin = 105.26% − 100% = 5.26%. That 5.26% is the cut.

Now the same match at a sharper price: - Player A: 1.96 → 1 ÷ 1.96 = 51.02% - Player B: 1.96 → 51.02% - Total = 102.04%, margin = 2.04%

Same contest, less than half the margin. On a $100 stake, the fair-value payout on a true 50% shot is $200. At 1.90 you get $190; at 1.96 you get $196. Over hundreds of bets that $6-per-win difference compounds into real money.

For a three-way football market (home / draw / away), you add three implied probabilities instead of two. A Serie A match priced 2.10 / 3.40 / 3.60 gives 47.62% + 29.41% + 27.78% = 104.81%, a 4.81% margin.

How margins differ by market and sport

Margins aren't uniform. Books load more juice where they have less confidence or where bettors are less price-sensitive.

• Main lines on major markets (NHL moneyline, NFL spread, NBA totals) tend to carry the thinnest margins because they're the most competitive and most bet.
• Niche props, same game parlays and futures carry fatter margins. Each leg of a parlay stacks its own overround, which is why a five-leg NFL Same Game Parlay can hide a compounded cut far larger than any single line.
• Live betting markets usually run wider margins than pre-match, because prices move fast and the book prices in uncertainty.

This is why comparing the same market across books matters more than chasing a single 'best odds' claim. A book can be sharp on NHL and pricey on tennis props at the same time.

Sampled margins across the books we track

We record average margins on sampled markets across Ontario-registered sportsbooks. These are observed averages from the samples noted — not guarantees, and they shift by sport and by day. Lower is better for the bettor.

• Pinnacle: 3.12% average margin, best price on 53.4% of sampled markets (221 markets)
• FanDuel: 4.06% average margin, best price share 23.5% (306 markets)
• DraftKings: 4.21% average margin, best price share 54.5% (898 markets)
• BetMGM: 4.69% average margin, best price share 14.6% (240 markets)
• Caesars Sportsbook: 5.35% average margin, best price share 36.7% (784 markets)
• Unibet: 5.74% average margin, best price share 8.5% (201 markets)
• Betway: 6.09% average margin, best price share 12.0% (191 markets)
• BetRivers: 6.28% average margin, best price share 18.9% (280 markets)
• 888sport: 6.63% average margin, best price share 9.2% (251 markets)
• LeoVegas: 6.86% average margin, best price share 6.0% (167 markets)

Two things stand out. Pinnacle posts the lowest average margin in our sample (3.12%) — consistent with its low-margin, high-volume model — which is why its odds rating sits at 9.4, the highest of any book here. And DraftKings leads on best-price share (54.5% of a large 898-market sample), meaning it topped the market more often than anyone else even though its average margin (4.21%) is fractionally above FanDuel's (4.06%). Best-price share and average margin measure different things: one is how often a book wins the line, the other is how much it charges on average. A book can win often on main lines while still charging more on the markets it doesn't lead.

Why the difference matters for your bankroll

Margin is the single biggest long-run drag on a bettor's returns, and it's the one thing you can actually control before a ball is bowled. You can't control variance. You can control which price you take.

Consider a bettor placing 200 bets of $50 across a season on two-way markets. On a book averaging 6% margin they're conceding roughly twice the theoretical hold of a book averaging 3%. That difference doesn't show up on any single slip — it shows up in the size of the account at season's end.

This is the practical case for line shopping: pulling up the same NHL or NBA game across two or three books and taking the shortest margin available. Our betting odds pages and comparison tools exist for exactly that — checking the actual price on the actual fixture before you commit.

How to reduce the margin you pay

• Compare the same market across books before betting. The best-price share numbers above show no single book leads every time.
• Stick to main lines where you can. Moneylines, spreads and totals on major competitions carry the tightest margins; heavy prop and parlay markets carry the most.
• Be cautious with Same Game Parlays. Each leg adds its own overround, so the combined margin is much larger than it looks.
• Watch live markets. In-play margins are typically wider than pre-match, so the convenience of betting live has a cost.
• Use a margin check on close markets. Sum the implied probabilities (1 ÷ decimal odds) for all outcomes; anything much above 105% on a main two-way market is on the pricey side.