Percentages (general terms )

Bookmakers set their odds according to percentages, the lower the percentage, the better deal the punter is getting. To calculate the percentage each price is worth, add a point and divide into 100. So 3/1 becomes four into 100, equals 25. A perfectly round book, with each price representing the true chance, would total 100. A book totalling 125 would be 25 percent over-round and give bookmakers a theoretical profit of 20 percent (25 divided by 125). In general, the bigger the field, the more the percentage favours the bookmakers.