از std::distance استفاده کنید .
مثال :
#include <iostream>
#include <vector>
#include <algorithm>
int main(){
std::vector<int> arr = { 1, 2, 30, 12, 50};
std::vector<int>::iterator loc = std::find(arr.begin(), arr.end(), 12);
std::vector<int>::iterator beg = arr.begin();
std::cout << std::distance(beg,loc);//3 chap mishe
}