How big will my 10 week old Chihuahua get? Her mom is 4 lbs and her dad is 3 1/2. She is the runt of the litter.

Hey Sarah....I have bred and shown Chihuahuas for over 20 yrs and I can tell you there is no way of guarantee of the size of your baby...you first must know her bloodlines. She maybe the runt of the litter but it cannot guarantee her size even by her parents size. Once you know how much she weighs now you can use this chart I am giving you the link for and it will give you a round about estimate of your babies growth. I am attaching an estimated Chihuahua wieght chart link for you. You may have to copy and paste it into another web search browser...hope this helps and If you have ANYMORE questions feel free to ask...
www.ahkennel.net/weightchart.htm

There is no way to predict the final size. You can only guess that it will be somewhere between the parents.

A rough estimate for adult weight is to multiply the 6 week weight by 4 or the 12 week weight by 2. That is an estimate though and will vary slightly from breed to breed.