4months old Fang.... is he too big or too small or right size for his kinds?

Fang is half Akita, and half german shepherd(dad is purebred german shepherd, mother is purebred akita).... Fang is rescued and moved into my family, he is now 4 months old, and almost 40pounds, basically almost half Aang(my other dog)'s size.... i am not certain if hes BIG for his kinds or ?????Aang is wolf/whippet/white german shepherd, weights at 87pounds(almost 4yrs old), stood 5'8" tall)

You might have to ask the vet for sure, but my brother has a 4 month old lab mix that weighs almost 40 pounds

Your vet should really be answering this question for you. The dog should be the right weight for HIS SIZE, not his breed. That's why growth charts and guesstimates can be so far off. At about 4 months, my GSD was just over 22lbs. He's now 85lbs at a year and a half. That puts your dog at enormous compared to my dog's growth rate. I know that one of the GSD enthusiasts on here thinks that 30lbs at 3 months is about right, putting your dog about on target for his growth chart. It's all about the individual dog/puppy and how he's developing.