The best place to start is the half point calcuator
http://www.sportsbookreview.com/Betting+Tool...alculator.aspx
In the specific example you mention, the correct odds for your bet (after the line has moved) would be -171, meaning the probability of winning is 63.1%. On the basis that you have made this bet at -110, you would calculate your EV as follows:
Probability of winning the bet
divided by
Implied probability at odds taken
minus 1
i.e 63.1%/52.4% = 1.204
minus 1 =
= 0.204
Expressed as a percentage, you have a +EV of 20.4%
When using Kelly your edge or the probability is an estimate based on your own handicapping or modeling.