Convert Octal to Decimal in C

In this source code example, we will write a code to convert the Octal to a decimal number in the C programming language.

Convert Octal to Decimal in C

In this C program, we will take input from the User or console and print the result to the output: 

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

// Converts octal number to decimal
int convertValue(int num, int i) { return num * pow(8, i); }

long long toDecimal(int octal_value)
    int decimal_value = 0, i = 0;

    while (octal_value)
        // Extracts right-most digit and then multiplies by 8^i
        decimal_value += convertValue(octal_value % 10, i++);

        // Shift right in base 10
        octal_value /= 10;

    return decimal_value;

int main()
    printf("Enter octal value: ");

    int octal_value;

    scanf("%d", &octal_value);

    long long result = toDecimal(octal_value);

    printf("%d in decimal is %d\n", octal_value, result);

    return 0;


Enter octal value: 12
12 in decimal is 10


Convert Octal to Decimal in C