Can I determine my peke's adult weight?

Does anyone know if there is a way to predict a peke's adult weight? My mom just bought a pomeranian and there is this formula to figure out their weight that many breeders use. Is there something similar for pekes? My puppy is almost 5 months, male neutered and he's approx 10 lbs now. I have no idea of his parent's weight b/c I got him from a pet store. I'm just so curious to know how big he'll be. If anyone knows, please fill me in.