This question have a great answer with all the guidelines for drilling holes in joists.
The question: Are the guidelines the same for band joists?
A bit of context: I'd like to add an exterior outlet for my central vaccuum cleaner and the shortest path is through the band joist. But I'm not sure if I can drill a 2 1/2" hole in a 7" band joist.
If the guidlines applies (and are not more restrictive either), the maximum hole size would be 2 1/3 inches. I can get by with a smaller hole, but I'd have to get another hole drill bit.