Market percentage in horse racing is the total of the win chances a race's prices imply: 1 divided by each runner's decimal odds, added up across the field. A fair market adds up to exactly 100%, so a race totalling 111% carries 11 points of bookmaker margin spread across its runners.
The figure reads the whole race at one moment: how short the average price is, not which runner is badly priced. How betting odds work explains the probability behind each price.
How to work out a race's market percentage
Divide 1 by one bookmaker's win price for every runner still in the race, and add the results. With illustrative prices from Bookmaker A near the jump in an 8-runner race:
| Runner | Price | Implied chance |
|---|---|---|
| Runner 1 | $3.25 | 30.8% |
| Runner 2 | $4.20 | 23.8% |
| Runner 3 | $5.50 | 18.2% |
| Runner 4 | $7.50 | 13.3% |
| Runner 5 | $11.00 | 9.1% |
| Runner 6 | $14.00 | 7.1% |
| Runner 7 | $18.00 | 5.6% |
| Runner 8 | $31.00 | 3.2% |
| Market | 111.1% |
Working: 1 / 3.25 = 0.308, 1 / 4.20 = 0.238 and so on down the field. The eight add up to 1.111, a market percentage of 111.1% and a margin of 11.1 points.
To back every runner to return $100, you stake 100 / price on each: $30.77 on Runner 1, $23.81 on Runner 2 and so on, down to $3.23 on Runner 8. The stakes come to $111.11, and whichever runner wins, $100 comes back.
So the market percentage is the cost of backing the whole field to collect $100, the idea behind dutching. If the margin were spread evenly, each $1 bet here would return 100 / 111.1 = about 90 cents on average.
What the total tells you, and what it does not
- It measures the margin across the whole race, so two bookmakers' totals on one race at one moment show which charges more on average.
- It tends to grow with the field, and the extra is a real cost: with the margin spread evenly, an illustrative 14-runner race at 125% returns 100 / 125 = 80 cents per $1 on average, against 100 / 110 = about 90.9 cents for a six-runner race at 110%.
- It does not show where the margin sits: one runner can be poor value inside a modest total or generous inside a high one.
- It needs the exact field: a missing runner pulls the total down, and a scratched runner left in pushes it up by its implied chance.
Bookmaker margin compares other market types, and the bookmaker margin calculator totals a field from its prices.
Why early race markets often run high percentages
Total the same race in the morning and again near the jump. With illustrative prices from Bookmaker A:
| Runner | Early price | Near the jump | Move |
|---|---|---|---|
| Runner 1 | $3.40 | $3.25 | Firmed |
| Runner 2 | $3.80 | $4.20 | Drifted |
| Runner 3 | $4.80 | $5.50 | Drifted |
| Runner 4 | $8.00 | $7.50 | Firmed |
| Runner 5 | $9.00 | $11.00 | Drifted |
| Runner 6 | $10.00 | $14.00 | Drifted |
| Runner 7 | $13.00 | $18.00 | Drifted |
| Runner 8 | $26.00 | $31.00 | Drifted |
| Market | 121.7% | 111.1% |
The early column adds up to 1.217 (1 / 3.40 + 1 / 3.80 and so on). At 121.7%, each $1 bet returns about 82.2 cents on average if the margin is spread evenly (100 / 121.7), against 90.0 cents near the jump (100 / 111.1). Three things push early totals up:
- Little money and information. An opening price is the bookmaker's estimate before much has been bet, so it leaves itself more room, and horse racing flucs shows how far thin early markets can move.
- News still to come: a scratching, a track rating change or a rider change can arrive after the market opens.
- Informed money. Wider prices limit what an early bet from someone who knows more than the bookmaker can cost it.
A higher early total does not make every early price worse: Runners 1 and 4 were longer in the morning. To test the pattern, total one race at one bookmaker at two times, and note the times.
Bookmaker markets compared with the exchange
On a betting exchange, the prices come from punters backing and laying with each other. The exchange earns commission from net winnings rather than from a margin in its prices, so its totals sit much closer to 100%. With illustrative exchange prices for the same race near the jump:
| Runner | Back price | Implied | Lay price | Implied |
|---|---|---|---|---|
| Runner 1 | $3.40 | 29.4% | $3.50 | 28.6% |
| Runner 2 | $4.60 | 21.7% | $4.70 | 21.3% |
| Runner 3 | $6.20 | 16.1% | $6.40 | 15.6% |
| Runner 4 | $8.40 | 11.9% | $8.60 | 11.6% |
| Runner 5 | $10.00 | 10.0% | $10.50 | 9.5% |
| Runner 6 | $15.50 | 6.5% | $16.50 | 6.1% |
| Runner 7 | $24.00 | 4.2% | $26.00 | 3.8% |
| Runner 8 | $46.00 | 2.2% | $55.00 | 1.8% |
| Market | 102.0% | 98.3% |
Back prices add up to a little over 100% and lay prices to a little under, and the exchange's view of each chance lies between the two. Bookmaker A's 111.1% is 9.1 points above the back side. Best prices taken runner by runner from several bookmakers total no more than any one bookmaker's, as which bookmaker has the best odds shows.
Commission closes some of that gap. At an illustrative 5% rate, a winning back bet at $3.40 is worth 1 + 2.40 x 0.95 = $3.28, and the eight back prices worked that way add up to about 106.3%, still below 111.1%. Betting exchanges in Australia covers backing, laying and commission.
Using market percentage to spot generous prices
Inside a 111.1% book most prices sit below the exchange's, but not all of them. To find the exceptions:
- Divide the runner's implied chance by the bookmaker's total. Runner 5 at $11.00 implies 9.09%, and 9.09 / 1.111 = 8.2% of Bookmaker A's book.
- Take the exchange's view of the same chance. The midpoint of 10.00% (back $10.00) and 9.524% (lay $10.50) is 9.762%, a fair price of 1 / 0.09762 = $10.24.
- Measure the bookmaker's price against it: edge = 11.00 / 10.24 - 1 = 7.4%.
Bookmaker A rates Runner 5 lower than the exchange does, which is why its price is longer, and value betting on horse racing works the same comparison in expected value.
Check the time on every price before you read a gap as value. A stale bookmaker price, a runner about to be scratched or a thin early exchange market can each produce a gap that is not really there.
Risk: Betting involves risk. Beating the exchange's estimate pays off only on average, the exchange can be thin or slow to move, and on these numbers Runner 5 still loses about 90 races in 100. See responsible gambling for limits and support.
Place market percentages
A place market is measured against the number of places paid, because that many runners will place: a fair three-place market adds up to 300%, and a two-place market 200%.
Under BR 18 of the Racing NSW Rules of Betting (checked October 2026), which bind NSW on-course bookmakers, a place-only bet is paid on the first three finishers if eight or more runners are in the race when it is made, and on the first two with five to seven. Online bookmakers write their own place terms, so check yours before you total a market. With illustrative place prices from Bookmaker A for the same race:
| Runner | Place price | Implied chance of placing |
|---|---|---|
| Runner 1 | $1.40 | 71.4% |
| Runner 2 | $1.65 | 60.6% |
| Runner 3 | $1.90 | 52.6% |
| Runner 4 | $2.20 | 45.5% |
| Runner 5 | $2.80 | 35.7% |
| Runner 6 | $3.30 | 30.3% |
| Runner 7 | $4.50 | 22.2% |
| Runner 8 | $7.00 | 14.3% |
| Market | 332.6% |
Against a fair 300%, the market runs 332.6 / 300 = 1.109, about 10.9% over. If that margin were spread evenly, a $1 place bet would return 300 / 332.6 = about 90.2 cents on average.
Compare a place total only with another place market that pays the same number of places. BR 18 counts the field when the bet is made, so a bet struck with eight runners keeps three places after a late scratching. Other rule books and bookmakers' terms can count it differently, as place betting covers.
What a late scratching does to the percentage
Take Runner 3 out of Bookmaker A's market after betting has opened. Its $5.50 price carried 18.2 points of the 111.1%, so the seven runners left add up to 92.9% until the prices are framed again. A total under 100% here is not a bargain, just a market with a hole in it.
New prices are framed for bets struck after the scratching. Winning fixed-odds bets struck before it can be cut instead by a deduction in cents in the dollar, which the race-day Stewards declare.
Racing NSW's policy note (checked October 2026) ties the deduction to the market percentage. Since 1 August 2011, New South Wales, the Northern Territory, Queensland and Victoria have used an algorithm whose job is to put the market percentage back where it stood before the withdrawal. Runner 3's 18.2 points leave a far bigger hole to fill than Runner 8's 3.2, so its withdrawal moves the other prices much further.
Deductions differ by bet type and by runner, and your bookmaker's terms say how it applies them: scratching deductions works through both methods.
Mistakes reading a race's market percentage
| Mistake | What goes wrong | The fix |
|---|---|---|
| Comparing totals across different fields | A fair field totals 100% at any size, so the gap is all margin, and bigger fields tend to carry more of it at every bookmaker | Compare bookmakers on the same race at the same moment |
| Leaving a scratched runner in | Its price inflates the total by its implied chance: 18.2 points for Runner 3 | Total only the runners still in the race |
| Measuring a place market against 100% | 332.6% reads as 232.6 points of margin instead of 10.9% over a fair 300% | Measure against the places paid |
Race markets side by side on the B337 Terminal
B337's Terminal covers thoroughbred, harness and greyhound racing. Each bookmaker gets its own column, runner by runner, with the best available price picked out. Betfair back and lay sit next to the bookmaker columns, with price history (flucs) and closing lines on the same board.
Not every bookmaker prices every race, so check that a column is complete before you add it up. Prices are refreshed on a repeating cycle rather than tick by tick, so confirm a price with your bookmaker before you bet.
A free account opens a limited view of the Terminal with live odds; Betfair prices and closing lines start with Terminal View. Bookmaker names are trade marks of their owners. B337 is not affiliated with them.
For free and confidential support call 1800 858 858 or visit gamblinghelponline.org.au.
Risk: Betting involves risk. A tight race market or a price above the exchange helps only on average: each bet still wins or loses in full, and a bookmaker can restrict an account or void bets under its terms.