How page table size calculate when virtual address space and page size and page table entry size given?

To calculate the page table size, divide virtual address space by page size and multiply by page table entry size.

Example: for a 120MB address space with a 4KB page size, you require 30,720 page table entries. If a page table entry is 4 bytes, you require a total page table size of 122,880 or 120KB.