Let’s use round numbers for simplicity.
There is $1000 in the win pool of an 8 horse field. The $1000 breaks down like this:
#1 – 500
#2 – 120
#3 – 100
#4 – 80
#5 – 80
#6 – 60
#7 – 40
#8 – 20
To calculate win odds, first the take-out must be deducted from the win pool. At 20%, this leaves $800 to pay to the winner. Win odds are then calculate this way:
#1: $800 total pool minus $500 winning dollars leaves $300 worth of losing dollars to pay the winners. This is 300/500 or 0.6, so for every $1 bet $0.60 is paid, for odds of 3/5.
The rest are calculated like this:
#1: 800-500 = 300 300/500 = 0.6 or 3/5 odds
#2: 800-120 = 680 680/120 = 5.7 or 5/1 odds
#3: 800-100 = 700 700/100 = 7.0 or 7/1 odds
#4: 800-80 = 720 720/80 = 9.0 or 9/1 odds
#5: 800-80 = 720 720/80 = 9.0 or 9/1 odds
#6: 800-60 = 740 740/60 = 12.3 or 12/1 odds
#7: 800-40 = 760 760/40 = 19.0 or 19/1 odds
#8: 800-20 = 780 780/20= 39.0 or 39/1 odds
When there is a dead heat to win, the winning tickets for both winning horses are removed to determine how much is left in the pool. In this example let’s say the #1 and #7 finished in a dead heat to win.
#1: 800-(500+40) = 260 130/500 = 0.26 or 1/5 odds ($2.52 to win for $2 ticket)
#7: 800-(500+40) = 260 130/40 = 3.25 or 3/1 odds ($8.50 to win for $2 ticket)
Even though the #7 was 19/1, there was only $130 worth of losing tickets to pay the $40 worth of winning tickets. (There were $260 worth of losing tickets, but this gets split evenly between the two winning horses, or $130 each)
Using the same example, if there would have been a dead heat to win with the #6 and the #7, the payout out the #7 wouldn’t have been reduced as much as it was in the example with the #1 (Big favorite) because all the tickets on the #1 are losers, leaving a lot more money to be paid to the winners.
#6: 800-(60+40) = 700 350/60 = 5.83 or 5/1 odds ($13.66 to win for $2 ticket)
#7: 800-(60+40) = 700 350/40 = 8.75 or 8/1 odds ($19.50 to win for $2 ticket)
I think........
