If you implemented this as follows, then yeah, you'll get log(N) reallocations, where N is your final vector size. But if you have a pretty good idea of what N

If you implemented this as follows, then yeah, you'll get log(N) reallocations, where N is your final vector size. But if you have a pretty good idea of what N is, you should set capacity at the time of vector declaration to avoid useless reallocations. You shouldn't expect any library to make this sort of predictions for you. vector<T> vec; while(getData(v)) { vec.push_back(v); }