in May of 2012 I started going to the gym 4+ times a week doing 60% weights and 40% cardio.



I've lost a ton of weight and gained noticeable muscle tone. Not to mention I lift much more weight than when I first started.



I know my starting weight, starting BMI, current weight and BMI.



What else do I need to know to figure out how many lbs of muscle i've gained?

 

You really need to be taking skin fold measurements. From there you can measure your bodyfat %, and from there, how much lean muscle mass you've gained. Weights alone don't indicate a whole lot.

 

Go back in time and do a proper (read: in a big tank of water) body composition analysis and find out how much of your self was fat, then do it again now and run the maths.



BMI is a fraud to get State actions crammed down your throat, and its use is widespread because americans are increasingly lazy and ignorant, and don't like to be touched to do a proper set of measurements.