I found this helpful for getting to a percentage:
Quote:
Fractional odds
Fractional odds are generally the most traditional form of expressing betting odds. They are a simple reflection of the return you will receive for a particular amount bet. So for example, the odds of 5/2 (expressed as 5 to 2) means that for every 2 units that you bet, you will receive 5 back.
To convert fractional odds into their respective probabilities, we make the following calculation.
So in our example of odds of 5/2.
Implied probability = 2 / (5 + 2)
Implied probability = 2 / 7
Implied probability = 0.286
Multiplied then by 100 to express as a implied probability percentage of 28.6%
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http://www.bettingexpert.com/blog/how-to-convert-odds