C++ Array Library - size() Function


The C++ function std::array::size() is used to get the number of elements present in the array.


Following is the declaration for std::array::size() function form std::array header.

constexpr size_type size(); noexcept



Return Value

Returns the number of elements present in the array. This value is always same as the second parameter of the array template used to instantiate array.

Do not confuse with sizeof() operator which return the size of data type in bytes.


This member function never throws exception.

Time complexity

Constant i.e. O(1)


The following example shows the usage of std::array::size() function.

#include <iostream>
#include <array>

using namespace std;

int main(void) {

   array<int, 5> int_arr;        /* Array of 5 integers */
   array<float, 0> float_arr;    /* Array of 0 floats */

   cout << "Number of elements in int_arr   = " << int_arr.size() << endl;
   cout << "Number of elements in float_arr = " << float_arr.size() << endl;

   return 0;

Let us compile and run the above program, this will produce the following result −

Number of elements in int_arr   = 5
Number of elements in float_arr = 0