The amount of clams you need per person depends on whether it's a main serving or you're serving the clams as an appetizer.
If you're serving the clams as a main serving then you should serve 1 lb of clams per person and if you're serving the clams as an appetizer you should serve 1/2 lbs of clams per person.
There are around 7 to 10 lbs of clams in one pound so you would serve each person 7 to 10 clams as a main course and for an appetizer you would serve each person 3 to 5 clams as an appetizer.
There are between 200 to 400 clams per bushel of clams depending on the type of clams you buy and serve.
Littleneck clams have around 400 clams per bushel and topneck clams have around 200 clams per bushel.