Question: how much weight do you gain from muscle?
Answer: The Skinny Guys Who Can't Gain Weight No Matter What They Do He says that you can expect to gain “about 0.2 to 0.25 pounds [of muscle] at most” in the first week. More depressingly for on-again, off-again exercisers, that applies as much to those who've taken some time away from the gym as it does to first-timers.