C Program to Convert Decimal to Octal

Decimal to octal conversion in C:

We can convert any decimal number (base-10 (0 to 9)) into Octal number(base-8 (0 or 7))  by c program.

Decimal Number

Decimal number is a base 10 number because it ranges from 0 to 9, there are total 10 digits between 0 to 9. Any combination of digits is decimal number such as 23, 445, 132, 0, 2 etc.

Octal Number

Octal number is a base 8 number because it ranges from 0 or 7. Any combination of digits (0 yo 7) is Octal number such as 34, 54, 77, 210 etc.

To understand this example, you should have the knowledge of the following C programming topics:

C Functions
C User-defined functions

#include <stdio.h>
#include <math.h>

int convertDecimalToOctal(int decimalNumber);
int main()
    int decimalNumber;

    printf("Enter a decimal number: ");
    scanf("%d", &decimalNumber);

    printf("%d in decimal = %d in octal", decimalNumber, convertDecimalToOctal(decimalNumber));

    return 0;

int convertDecimalToOctal(int decimalNumber)
    int octalNumber = 0, i = 1;

    while (decimalNumber != 0)
        octalNumber += (decimalNumber % 8) * i;
        decimalNumber /= 8;
        i *= 10;

    return octalNumber;


Enter a decimal number: 78
78 in decimal = 116 in octal

Enter a decimal number: 10
10 in decimal = 12 in octal

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