Fundamentals Are Strong, page-148

Hey I'm on my phone atm and don't have my spreadsheet, but here is the general idea:

Share Price / Earnings per share = PE

PE / Growth Rate = PEG

Share Price / PEG = Fair value

One traditionally uses a weighted average of Earnings Per Share to calculate growth rate. There is a bit of a fudge factor for a company like MYX because the massive acquisition means that the historical rate of growth isn't organic - I've used a weighted average of other American generics companies, with 50% of the pre-Teva acquisition growth rate to approximate MYX's. You could also use revenue growth rather than EPS if you felt your target company was more like a start-up than an established player.