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.
