size_type capacity () const;

Return size of allocated storage capacity

Returns the size of the allocated storage space for the elements of the vector container.

Notice that, in vectors, the capacity is not necessarily equal to the number of elements that conform the underlying vector content (this can be obtained with member vector::size), but the capacity of the actual allocated space, which is either equal or greater than the content size.

Notice also that this capacity does not suppose a limit to the size of the vector. If more space is required to accomodate new elements in the vector, the capacity is automatically expanded, or can even be explicitly modified by calling member vector::reserve.

The real limit on the size a vector object can reach is returned by member vector::max_size.

Parameters

Return Value

Member type size_type is an unsigned integral type.

Example

// comparing size, capacity and max_size
#include <iostream>
#include <vector>
using namespace std;

int main ()
{
  vector<int> myvector;

  // set some content in the vector:
  for (int i=0; i<100; i++) myvector.push_back(i);

  cout << "size: " << (int) myvector.size() << "\n";
  cout << "capacity: " << (int) myvector.capacity() << "\n";
  cout << "max_size: " << (int) myvector.max_size() << "\n";
  return 0;
}

A possible output for this program could be:

size: 100
capacity: 141
max_size: 1073741823

Complexity

See also