This exacta harville method calculator is based on Harville’s Method (Harville, D.A. (1973) Assigning probabilities to the outcomes of multi-entry competitions.).
Harville’s method assumes that horse that won is automatically discounted from placing and the win probabilities of the remaining horses are adjusted back to 100%.
The win probabilities do not determine the probability that horse x finishes in position y.
These are totally unrealistic assumptions and should not be used in betting purposes as such. But do provide rough estimates that can be used on the race track.

What Are Exacta Bets?
Exacta bet involves predicting the first two finishers in the correct order. You choose which horses you think will come in first and second place. More about harness racing basics:

Exacta Calculator

Select the number of runners on the race (between 2 and 25):

Enter win probabilities for each runner (sum of the probabilities must be 100%):

Calculated Harville Probabilities:

Exacta Combination Probability Implied Decimal Odds