Thanks for all the help, I'll just stick with eating more than normal and see how I am in month and go from there

Whats the best equation for figuring out how much you need a day? I've been on various websites and have got different answers.

I am 20 years old, 5'9'' at 150lbs, and have never been able to gain weight. I want to put on some mass while keeping the six pack I've just always had. I just started lifting heavy with low reps 3...