Convert Decimal to Binary in C++

In this tutorial, we will learn how to convert a decimal number to binary in C++.

Decimal number is a base 10 number as it ranges from 0 to 9. There are 10 total digit choices we can accommodate in a decimal number.
Whereas a binary number is a base 2 number. It has only two-digit choices, 0 and 1. Every binary number is composed of 0s and 1s.

Theoritcally, we convert decimal to binary as follows:

  • Suppose the assumed number is 12.
  • Divide 12 by 2. The remainder is 0 and the new number is 6.
  • Divide 6 by 2. The new value is 3 and the remainder is 0.
  • Divide 3 by 2. The new value is 1 and the remainder is 1.
  • Once the value reaches 1, we stop, and the answer is 1100.

The same approach is used while converting decimal to binary in C++.

C++ Code: Convert Decimal to Binary

using namespace std;
void decToBi(int n)
    int arr[64];
    int i=0;
    for(int j=i-1; j>=0; j--)
int main()
    int n = 12;
    cout<<"Decimal number is: "<<n;
    int ans = decToBi(n);
    cout<<"Binary equivalent: "<<ans;
    return 0;
Decimal number is: 12
Binary Equivalent: 1100

The explanation to this code is very simple. Have a look if you find the code confusing.

  • As the theoretical conversion is explained, the code is very similar to it. The remainder values are used to store the answer.
  • An array, arr[], is used to store these remainder values.
  • n is divided by 2 each time and the remainder is stored.
  • The process is continued till n>0.
  • Once the condition fails, the array is printed in reverse order to get the required answer.


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