Hi,

Can anyone help with a formula for converting rating figures to odds (such as Sportsman Zip or QldTAB ratings).

I was using - total all ratings and divide the individual by the total for a percentage which is easily converted to odds - where this seems to come undone is...
5 horses with ratings 100,80,80,80,80,80 for a total of 420, so horse 1 has 23.8% chance of winning.
Now add another 5 horses all rated at 80 each to the above and re-calculate horse 1 - we get horse 1 with 12% chance to win.

If the above #1 horse was Lohnro, the diffreence in winning percentage seems incorrect.