A quick way to calculate parlay odds of underdogs and its hedging odds
By using a simple calculator.
For two dogs +123 and +456, the parlay odds of them is: 223 * 5.56 - 100 = +1140
If the favorite odds opposite to the above dogs are -133 and -470, then the hedging odds of the above parlay is 233 * 5.70 - 100 in negative value = -1228
Note the leading number increment by 1 in calculation: 1->2 and 4->5.