Being an engineer who have no background in accounting (just got a few terms from my engineering economy subject), I devised my own way of measuring the profitability of my stocks using a little math and the power of Excel. It sounds easy but for me who injects money in my portfolio at an irregular basis with no definite amount and wants an accurate effective real-time return, I made it a little complex. I'm sure there's a simpler way so if you know it, please drop me a mail at ramon.tubero@gmail.com.
Here's how my formula goes:
Effective annual rate of return = (Total profit or loss x 365)/{Sum of (the amount of deposit x no. of days since the deposit was made)}.
If you want a copy of my Excel spreadsheet or you think that my computation is wrong, just email me on tubero.ramon@gmail.com