How many weeks does it take newborn puppies to grow bigger?

I think it's when it is about 2 weeks old,or 6 weeks old.So if you have a newborn puppy and you wanna know when it grows fur and gets smarter(and stuff)all you have to do is this:

1.Check the first two weeks.

2.If he/she didn't grow fur yet,wait more.

3.Check four weeks later(If you don't get it add 4+2.4+2=6)to see if it grew fur NOW.