How long do they grow?

Cosmo (my big ole 2.5 yr old Cav) has finally warmed up to Buster (3.5 month old Cav). I was worried about Cosmo as he was totally stressed for a while. I still think that he has further to go, but he's heading in the right direction.

The one thing that I don't remember is how old Cosmo was when he stopped growing. The size difference now is huge, as Cosmo weighs around 27 lbs and Buster about 4.5 lbs. How old typically do Cavs grow until?

Buster is already on the small size for his age but how big he gets depends on litter size, average family size over a couple of generations, etc.

He will reach most of his final size by age 1, but males keep filling out til over two years of age, breeders say. However Jaspar and Leo have stayed pretty much the same size and weight since they were about one. Intact males probably will fill out more to a later age than neutered males, I am guessing.

Buster will probably grow rapidly for another 3-4 months then slow down.

Growing

From what I have experienced, most dogs will grow to size by about 18 months. Some take a little longer to fill out (maybe up to 2 years, but this is usually for bigger dogs) but generally 18 months you have what you will for the years to follow.

Some Cavaliers have quite a slight bone structure and so can look quite small (thin) but are still the same height of wider dogs. Steralised dogs and bitches may be slightly smaller that their intact cousins (if they have been done early in life) because growing doesn't go on for much longer after being snipped, this doesn't apply if they are opperated on after 9 months/1 year because almost all the growing is done by this time.

A 3.5 month old pup will grow quite a bit for the next while (and this can be seen to slow down the older they get) so you may end up with a monster! An awful lot of it has to do with genetics and good feeding (i.e. if a pup is genetically inclined to be big but had a dodgy start and was starved, the pup could be very small for its age. If decent nutrition is then introduced the rapid growth period will be delayed and the pup can be smaller than it is genetically designed to be, or may be reach size with no problems - it really depends on the pup. A perfect example is a runt in a littler; some become bigger than their siblings and others stay quite relatively small) Generally, puppy size is an approximation of the size of the adult but sometimes they can surprize you!