Calculating Size of model

I want to know the size of the model for comparison between the models. For quick check i sometimes look the size of bin files of model but sometime there are more than one bin file what does it tell? For instance alpaca 7b and vicuna 7b are finetuned from llama 7b. But in model files they have different sizes of bin files. I know both models have same number of parameters which i checked using
sum(p.numel() for p in model.parameters()). Can somebody clarify why the file sizes do not match.
Alpaca snapshot