What does a bet actually cost?
We measured the bookmaker's built-in margin on 205,491 head-to-head betting
markets across 31 bookmakers and nine sports. On average the bookmaker keeps
$4.78 of every $100 staked — but where you bet changes that by more
than 80%.
Data collected 29 June – 27 July 2026 · Published 27 July 2026 ·
Free to reuse under CC BY 4.0 with attribution
83%
gap, cheapest to dearest
What "margin" means
Bookmakers do not charge a fee. Instead they price both sides of a market so the implied
chances add up to more than 100%. That surplus is the margin, and it is the cost of the
bet — the reason a coin-flip market pays less than even money on both sides.
If a market's two prices imply a 52.4% and a 52.4% chance, the total is 104.8%. The margin
is 4.8%, and that is what the bookmaker expects to keep.
This is not a claim that bookmakers are doing anything improper. A
margin is how they make money and it is stated openly in every price. The useful
question is not whether it exists but how much it varies —
because that part is within a bettor's control.
The average is 4.78%
Across all 205,491 markets, the mean margin was 4.78% and the median
4.71%. The two being close tells us the distribution is not being dragged
by a small number of extreme markets.
It varies by sport
Ice hockey and baseball were the cheapest sports to bet on. Tennis was the most expensive
— a tennis bet carried about 24% more margin than an ice hockey one.
| Sport | Markets | Average margin |
|---|
| Ice hockey (NHL) | 8,516 | 4.54% |
| Baseball (MLB) | 41,085 | 4.55% |
| American football (NFL) | 67,174 | 4.60% |
| College football (NCAAF) | 36,883 | 4.80% |
| Mixed martial arts (UFC) | 24,178 | 5.05% |
| Basketball (WNBA) | 8,270 | 5.08% |
| Australian rules (AFL) | 11,416 | 5.40% |
| Tennis (ATP) | 3,605 | 5.59% |
| Tennis (WTA) | 4,364 | 5.61% |
It varies far more by bookmaker
This is the finding that matters, because it is the one a bettor can act on. The same kind
of market, over the same month, priced very differently depending on who was offering it.
Lowest average margin
| Bookmaker | Markets | Average margin |
|---|
| lowvig | 4,238 | 3.16% |
| BetOnline | 7,881 | 3.61% |
| BetUS | 4,972 | 3.70% |
| Hard Rock Bet (FL) | 2,525 | 4.32% |
| Bovada | 8,484 | 4.33% |
| DraftKings | 21,380 | 4.33% |
Highest average margin
| Bookmaker | Markets | Average margin |
|---|
| MyBookie | 9,006 | 5.78% |
| Fliff | 2,278 | 5.72% |
| Rebet | 5,401 | 5.66% |
| Unibet | 4,122 | 5.62% |
| Betr (AU) | 4,159 | 5.52% |
| PlayUp | 3,437 | 5.46% |
The spread is 3.16% to 5.78%. In plain terms: stake $100 a week for a year
at the cheapest bookmaker in this sample and the built-in cost is about $164. Do exactly
the same thing at the most expensive and it is about $300. Same bets, same sports, same
month — $136 difference from the choice of bookmaker alone.
Betting exchanges are not in this table. Betfair's
exchange showed an equivalent figure of 2.47%, but exchanges charge a commission on
winnings rather than building the cost into the price, so the two numbers are not
measuring the same thing. It has been excluded rather than presented as a like-for-like
winner.
How this was measured
We continuously record publicly displayed betting prices for research. Between 29 June and
27 July 2026 that archive covered 4.27 million individual price observations.
From those we took every head-to-head market — a simple two-outcome
"who wins" market, chosen because it is the one market type that is directly comparable
across every sport and bookmaker. For each observation we converted both prices to implied
probabilities (1 ÷ decimal price), summed them, and subtracted 100%.
That figure is the margin.
What was excluded, and why
- Anything recorded after the event started. In-play prices behave
differently and would not tell a pre-match bettor anything useful.
- Markets without exactly two outcomes, so that three-way sports are not
compared against two-way ones.
- Margins below 0% or above 20% — 400 observations, 0.17% of the
total. Inspection showed these were suspended or near-settled markets where both
prices had collapsed, not genuine offers. Leaving them in would have inflated several
sports by multiples.
- Betting exchanges, for the reason given above.
That left 205,491 clean pre-match markets across 983 events and 31 bookmakers.
Limitations, stated plainly. This is one month of
data, so it describes that month rather than all time. Bookmakers price different
sports and competitions to different depths, so a book appearing expensive here may be
competitive in a market we did not sample. Margins move around major events. And
head-to-head is the tightest market bookmakers offer — margins on multis, player
props and exotic markets are materially higher, so 4.78% is a floor, not an
average across everything you can bet on.
Reusing this
The figures on this page are published under
CC BY 4.0. You may
quote, chart or build on them, including commercially, provided you credit the source.
Suggested citation:
Bet Better (2026). Bookmaker Margin Study: 205,491 head-to-head markets across 31
bookmakers. https://betbetter.world/studies/bookmaker-margins
We do not publish the underlying price observations. The archive is licensed from a data
provider under terms that permit publishing analysis derived from it but not
redistribution of the prices themselves. Everything on this page is aggregate output.
Our open datasets and free model API are available separately:
the model API and an
open AFL dataset.
18+. Gambling involves risk and most people lose money.
Nothing here is betting advice. Understanding the margin does not make betting
profitable — it explains why, on average, it is not. If gambling is causing you
harm, support is available at
Gambling Help Online (AU)
or 1-800-GAMBLER (US).