Formula #1
1/the price (rounded up)=the percentage of wins it takes to make a profit.
For example 1/1.90=.5263 or roughly 53%
So if you made 100 picks @1.90 you would have to win 53 of them to make a profit.
Formula #2
1/ your win percentage=the average price (rounded up)that you should be getting to make a profit
For example 1/.53=1.89
So if you made 100 picks and won 53% of the time you would have to be getting an average price of 1.89 to make a profit.