general rule is you double the wgt at 16 wks this is still a guess. but if your pup is 4 pounds at 3 months well your looking at 8 easliy. My ayla (morkie) she was 1 pound when I got her at 2 month and she is now 1 years old yesterday and she wgts about 6-7 pounds today. So it really depends. My yorkie who is 7 months has been holding 4.6 for over a month but they get spurts of growth so you just never know till they are done. Hope this helps
