Below is a copy of a post I've often made in responding to similar posts:
There's no meaningful average for Lab puppy weight gain because there are so many different lines and some young adults level off at 50 lbs (or less) while others level out at 125 lbs (or more).
I measured my Puff's weight gain regularly. Her rate of growth followed a curve similar to the silhouette of the NW quadrant of a US/Can football when its noses are pointed EW.
Reading off her growth curve (weight X Day's Age) I plotted:
At 65 days, she weighed 6 lbs. (65 dys = 2 mos, 5 dys)
At 105 days, 20 lbs. (3 mos, 15 dys)
At 145 days, 31 lbs. (4 mos, 25 dys)
At 185 days, 42 lbs. (6 mos, 5 dys)
At 225 days, 47 lbs. (7 mos, 15 dys)
At 265 days, 52 lbs. (8 mos, 25 dys)
At 305 days, 54 lbs. (10 mos, 5 dys)
At 2 years, 63 lbs.
A friend has a male Lab from a BYB; he was born on the very same date as Puff and always weighed twice what Puff weighed at the same age.
But I've seen a study published (in JAVMA) by vets at Seeing Eye in N.J., on growth rates for the Lab line they breed. Instead of being a concave curve like Puff's, theirs is sinusoidal (a stretched out S-shape): their Labs initially gain weight at a slower rate than Puff and her friend did for about the first 5 months, then accelerate more rapidly, and then level off.
So -- it all depends. There's no ONE pattern. Perhaps your Lab breeder has typical data for your line?
Puff [YF, AKC field line (from competing HT/FT breeder) 62 lbs, dob: 8-'01]
As others have said, growth depends on the particular lines and the breeder is probably the best source, but I just wanted to share some information about how Henna grew. I also was concerned when I starting meeting other lab puppies in classes and all of them looked much much bigger than my puppy. Then suddenly in a matter of 2 months she grew a lot and I only noticed it when she started hitting her head when trying to come underneath my desk :ugly:
This is the data:
You will find many posts about this here and I think the most import thing is to know if he is eating when served and that you still can easily feel his ribs but can't see them.
I've not found any standard growth pattern to apply from lab pup to lab pup. Even my two from the same litter look different, grow different, weigh different. They are getting weighed tonight in fact. But last time I did it, they were 14 weeks, Jack was 36# and Jed was 30#.