Decimal To Octal Conversion | C Program

January 19, 2026

Decimal to Octal Conversion in C

Here, in this section, we will discuss the Decimal to Octal conversion in C.

The C program to convert decimal to octal number accepts a decimal number from the user. This number is further converted to its equivalent octal number after following a series of steps. The following section gives an algorithm for this conversion. It is then followed by a C program.

Decimal-to-Octal-in-C-Program

Methods discussed

  • Using an array to store the comparable octal value
  • Using int variable to store comparable octal value

Method 1

C-Program-to-Convert-Decimal-to-Octal
While loop in C

Hexadecimal to Decimal conversion

Decimal to Binary conversion

Decimal to Octal Conversion

Decimal to Hexadecimal Conversion

Binary to Octal conversion

Octal to Binary conversion

C Program for Decimal to Octal Conversion

Run 
// C Program to convert Decimal to Octal using Array
#include<stdio.h>

void convert(int num)
{
    // creating an array to store octal equivalent
    int octalArray[32];
 
    // using i to store octal bit at given array position
    int i = 0;
    while (num > 0) {
 
        // resultant remainder is stored at given array position
        octalArray[i] = num % 8;
        num = num / 8;
        i++;
    }
 
    // printing octal array in reverse order
    for (int j = i - 1; j >= 0; j--)
        printf("%d",octalArray[j]);
}
 
int main()
{
    int n = 148;
    convert(n);
    return 0;
}

Output

224
While loop in C

Method 2

  • Rather than creating a temporary array
  • We will use a variable decimal to store the octal result
  • Will use a mathematical calculation to derive conversion into variable
C-Program-to-Convert-Decimal-to-Octal-method-2
While loop in C

Method 2 Code in C

Run
#include<stdio.h>

void convert(int num)
{
    int octal = 0;
    int rem, i = 1;
    
    while(num!=0)
    {
        rem = num % 8;
        num /= 8;
        octal += rem * i;
        
        // moving to next position ex: units -> tens
        i *= 10;
    }
    printf("%d",octal);
}
 
int main()
{
    int decimal_num = 221;
    convert(decimal_num);
    return 0;
}

Output

335

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2 comments on “Decimal To Octal Conversion | C Program”


  • J

    #include

    int main()
    {
    int n,decimal,rem,sum=0,base=1;
    printf(“enter a decimal number\n”);
    scanf(“%d”,&decimal);
    n=decimal;
    while(decimal>0)
    {
    rem=decimal%8;
    sum=sum+rem*base;
    decimal=decimal/8;
    base=base*10;
    }
    printf(“the octal format is %d “,sum);
    }
    simplest form for above progam