Bookmaker’s Overround
Bookmakers are profit making businesses. To keep them profitable they need to write in a certain amount of margin into each market they offer prices on. An overround of 110% means that the customer must stake a total of €110 spread out over all the selections to guarantee himself a return of €100 regardless of the result. In this way the bookmaker expects to make a profit of €10 for every €110 turnover.
We will first look at how margin is calculated:
For odds displaying in the fractional form X/Y the margin on this is calculated using the formula Y/(X+Y). e.g. the margin on 6/4 = 4/(6+4) = 4/10 = 40%.
For odds displaying in the decimal format this calculation is even easier as you just divide 1 by the decimal and display as a percentage. e.g. the margin on 2.5 (this is the decimal form of 6/4) is 1/(2.5) = 40%.
So if a bookmaker offers odds on a 3-way market with odds on the 3 selections of 1/1 (=50%), 2/1 (=33.33%) and 3/1 (=25%). This results in an overround of 108.33%.
The size of the overround depends on the number of selections and how high profile the event is. These can range from approximately 104% for the Superbowl match betting, 106% for Premier League Soccer match betting, 111% on lower profile soccer leagues, 125% on greyhound races with 6 selections, 130% on soccer correct score market to in the region of 160% on a golf tournament with over 100 golfers. The higher the overround the more margin the bookmakers expect to make from a market, making it increasingly difficult for the bettor to have a profitable bet.
Genie recommends
- Global sportsbook & casino.
- Punt with over 20 cryptocurrencies + fiat.
- Frequent promotions & cashback offers.
- Global availability & language support.
- Over 3,000 casino games & live casino.
Find out more

Fractional and decimal odds margin chart
Please see Genie’s chart that converts prices from fractional to decimal odds and displaying the margins on these odds.
FRACTIONAL ODDS | DECIMAL ODDS | MARGIN |
1/100 | 1.01 | 99.01% |
1/66 | 1.02 | 98.51% |
1/50 | 1.02 | 98.04% |
1/33 | 1.03 | 97.06% |
1/25 | 1.04 | 96.15% |
1/20 | 1.05 | 95.24% |
1/16 | 1.06 | 94.12% |
1/12 | 1.08 | 92.31% |
1/10 | 1.10 | 90.91% |
1/9 | 1.11 | 90.00% |
1/8 | 1.13 | 88.89% |
1/7 | 1.14 | 87.50% |
1/6 | 1.17 | 85.71% |
1/5 | 1.20 | 83.33% |
2/9 | 1.22 | 81.82% |
1/4 | 1.25 | 80.00% |
2/7 | 1.29 | 77.78% |
3/10 | 1.30 | 76.92% |
1/3 | 1.33 | 75.00% |
4/11 | 1.36 | 73.33% |
2/5 | 1.40 | 71.43% |
4/9 | 1.44 | 69.23% |
1/2 | 1.50 | 66.67% |
8/15 | 1.53 | 65.22% |
4/7 | 1.57 | 63.64% |
8/13 | 1.62 | 61.90% |
2/3 | 1.67 | 60.00% |
8/11 | 1.73 | 57.89% |
4/5 | 1.80 | 55.56% |
5/6 | 1.83 | 54.55% |
10/11 | 1.91 | 52.38% |
1/1 | 2.00 | 50.00% |
11/10 | 2.10 | 47.62% |
6/5 | 2.20 | 45.45% |
5/4 | 2.25 | 44.44% |
13/10 | 2.30 | 43.48% |
11/8 | 2.38 | 42.11% |
7/5 | 2.40 | 41.67% |
3/2 | 2.50 | 40.00% |
8/5 | 2.60 | 38.46% |
13/8 | 2.63 | 38.10% |
17/10 | 2.70 | 37.04% |
7/4 | 2.75 | 36.36% |
9/5 | 2.80 | 35.71% |
15/8 | 2.88 | 34.78% |
2/1 | 3.00 | 33.33% |
21/10 | 3.10 | 32.26% |
11/5 | 3.20 | 31.25% |
9/4 | 3.25 | 30.77% |
23/10 | 3.30 | 30.30% |
12/5 | 3.40 | 29.41% |
5/2 | 3.50 | 28.57% |
13/5 | 3.60 | 27.78% |
11/4 | 3.75 | 26.67% |
14/5 | 3.80 | 26.32% |
3/1 | 4.00 | 25.00% |
16/5 | 4.20 | 23.81% |
10/3 | 4.33 | 23.08% |
7/2 | 4.50 | 22.22% |
15/4 | 4.75 | 21.05% |
4/1 | 5.00 | 20.00% |
9/2 | 5.50 | 18.18% |
5/1 | 6.00 | 16.67% |
11/2 | 6.50 | 15.38% |
6/1 | 7.00 | 14.29% |
13/2 | 7.50 | 13.33% |
7/1 | 8.00 | 12.50% |
15/2 | 8.50 | 11.76% |
8/1 | 9.00 | 11.11% |
9/1 | 10.00 | 10.00% |
10/1 | 11.00 | 9.09% |
11/1 | 12.00 | 8.33% |
12/1 | 13.00 | 7.69% |
14/1 | 15.00 | 6.67% |
16/1 | 17.00 | 5.88% |
18/1 | 19.00 | 5.26% |
20/1 | 21.00 | 4.76% |
22/1 | 23.00 | 4.35% |
25/1 | 26.00 | 3.85% |
28/1 | 29.00 | 3.45% |
33/1 | 34.00 | 2.94% |
40/1 | 41.00 | 2.44% |
50/1 | 51.00 | 1.96% |
66/1 | 67.00 | 1.49% |
80/1 | 81.00 | 1.23% |
100/1 | 101.00 | 0.99% |
125/1 | 126.00 | 0.79% |
150/1 | 151.00 | 0.66% |
200/1 | 201.00 | 0.50% |
250/1 | 251.00 | 0.40% |
300/1 | 301.00 | 0.33% |
400/1 | 401.00 | 0.25% |
500/1 | 501.00 | 0.20% |
750/1 | 751.00 | 0.13% |
1000/1 | 1001.00 | 0.10% |