Chihuahuas usually reach their maximum length and height by the time they are 6 months old. However, from there they will put on the muscle and weight that finishes their growth. So, if your Pup is 2.8 pounds at 3 months I would estimate that he/she will end up being around 5 pounds fully grown. This is of couse an estimate because I don't know the size of the parents, whether he/she has a molera, or how many puppies were in the litter. Hope this helped!
Sorry I didn't post back sooner Nadia. If a Chi's molera doesn't close in a timely fashion it will inhibit their growth potential. That is why so many of the really small Chi's usually have large open fonts (moleras).
So that is why the molera effects their size (not just their weight).
As well-intentioned as that chart is...I have found that 9 times out of 10 it is wrong. Too many different factors that determine a Chihuahua's size for any chart to be accurate.
***Edited By: PuPzRuS on 1/5/2006 5:44:50 PM*** Reason: add