I have a German Shepherd/Cocker Spaniel mix and I was wondering how big he might be.

First off how old is your dog now? If it is still less than one year old - then I would go by the paw size. A German Shepard is usually around 60+ lbs and a Cocker is around 35-40. My best guess would be in the 50 lbs range if the paws are on the big side and 40 lbs if the paws are smaller and more delicate.

Just to give you a little perspective. I have a german shepherd/cocker spaniel mix and he is a little over a year old. He is only a little over 20lbs right now, he's tall and skinny.

Hope that helps a little