this can't be quantified. It depends on way too many factors:
1) your current weight
2) height
3) gender
4) current bf %
5) body type (ie. endomorph)
6) how long you have been training
7) the intensity and type of training you are doing
8) eating habbits
For example, a 6'2 endomorph male, weighing in at 180 lbs with 20% BF that just started training would probably be able to put on 5lbs in a week of heavy training.
A 5'0" exomorph female, weighting 120 lbs with 12% BF that has been training for a year, it would probably take a few months.
Even given two people that seem identical, every person reacts differently to different training methods and type of foods consumed.
However, I will say this: if you have been working out for a while with no results, it is most likely because you aren't eating enough. You can't gain mucle if your body has nothing to use to create muscle.