Hi! Welcome to YT. You will have to post some pics of your precious Ruby.
Here is a growth chart
http://yorkiepassion.com/growthchart.htm
Also, I have been told there is a scale for determining approximate adult size at 8 and 12 weeks but it is not a 100% guarantee. Usually you triple the weight at 8 weeks and double it at 12 weeks.
There is a wealth of information available on this site. Feel free to browse around. I used a search and found all of this information.