When do German Spitzes stop growing?

When German Spitzes stop growing depends on the variety. There are toy, medium, and large German Spitz sizes. 

Toy German Spitzes stop growing around nine months of age. They reach their full height at about six months old and will continue to fill out for a few more months.

Medium German Spitzes stop growing around 12 months old, reaching their full height around nine to 10 months old, and gaining muscle mass until their first birthday. 

Large German Spitzes typically stop growing around 18 months. As the largest of the three, their growth may take a bit longer to finalize as they continue to build muscle and develop a strong, sturdy frame past the 12-month mark.