Program for Octal to Decimal Conversion

Given an octal number as input, we need to write a program to convert the given octal number into equivalent decimal number.

Examples:

Input : 67
Output : 55

Input : 512
Output : 330

Input: 123
Output: 83

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

The idea is to extract the digits of given octal number starting from right most digit and keep a variable dec_value. At the time of extracting digits from the octal number, multiply the digit with the proper base (Power of 8) and add it to the variable dec_value. At the end, the variable dec_value will store the required decimal number.

For Example:
If the octal number is 67.
dec_value = 6*(8^1) + 7*(8^0) = 55

Below diagram explains how to convert octal number ( 123 ) to equivalent decimal value:

Below is the implementation of above idea.

C/C++

// C++ program to convert octal to decimal 
#include <iostream> 
using namespace std; 
  
// Function to convert octal to decimal 
int octalToDecimal(int n) 
{ 
    int num = n; 
    int dec_value = 0; 
  
    // Initializing base value to 1, i.e 8^0 
    int base = 1; 
  
    int temp = num; 
    while (temp) { 
  
        // Extracting last digit 
        int last_digit = temp % 10; 
        temp = temp / 10; 
  
        // Multiplying last digit with appropriate 
        // base value and adding it to dec_value 
        dec_value += last_digit * base; 
  
        base = base * 8; 
    } 
  
    return dec_value; 
} 
  
// Driver program to test above function 
int main() 
{ 
    int num = 67; 
  
    cout << octalToDecimal(num) << endl; 
} 

Java

// Java program to convert octal to decimal 
import java.io.*; 
  
class GFG { 
  
    // Function to convert octal to decimal 
    static int octalToDecimal(int n) 
    { 
        int num = n; 
        int dec_value = 0; 
  
        // Initializing base value to 1, i.e 8^0 
        int base = 1; 
  
        int temp = num; 
        while (temp > 0) { 
            // Extracting last digit 
            int last_digit = temp % 10; 
            temp = temp / 10; 
  
            // Multiplying last digit with appropriate 
            // base value and adding it to dec_value 
            dec_value += last_digit * base; 
  
            base = base * 8; 
        } 
        return dec_value; 
    } 
  
    // driver program 
    public static void main(String[] args) 
    { 
        int num = 67; 
        System.out.println(octalToDecimal(num)); 
    } 
} 
  
// This code is contributed  
// by Pramod Kumar 

Python3

# Python3 program to convert  
# octal to decimal 
  
# Function to convert 
# octal to decimal 
def octalToDecimal(n): 
      
    num = n; 
    dec_value = 0; 
  
    # Initializing base value 
    # to 1, i.e 8^0 
    base = 1; 
  
    temp = num; 
    while (temp): 
  
        # Extracting last digit 
        last_digit = temp % 10; 
        temp = int(temp / 10); 
  
        # Multiplying last digit 
        # with appropriate base 
        # value and adding it  
        # to dec_value 
        dec_value += last_digit * base; 
  
        base = base * 8; 
  
    return dec_value; 
  
# Driver Code 
num = 67; 
print(octalToDecimal(num)); 
      
# This code is contributed by mits 

C#

// C# program to convert octal to 
// decimal 
using System; 
  
class GFG { 
      
    // Function to convert octal 
    // to decimal 
    static int octalToDecimal(int n) 
    { 
        int num = n; 
        int dec_value = 0; 
  
        // Initializing base value  
        // to 1, i.e 8^0 
        int b_ase = 1; 
  
        int temp = num; 
        while (temp > 0)  
        { 
              
            // Extracting last digit 
            int last_digit = temp % 10; 
            temp = temp / 10; 
  
            // Multiplying last digit  
            // with appropriate base  
            // value and adding it to  
            // dec_value 
            dec_value += last_digit 
                              * b_ase; 
  
            b_ase = b_ase * 8; 
        } 
        return dec_value; 
    } 
  
    // driver program 
    public static void Main() 
    { 
        int num = 67; 
          
        Console.WriteLine( 
                   octalToDecimal(num)); 
    } 
} 
  
// This code is contributed by vt_m. 

PHP

<?php 
// PHP program to convert octal to decimal 
  
// Function to convert 
// octal to decimal 
function octalToDecimal($n) 
{ 
      
    $num = $n; 
    $dec_value = 0; 
  
    // Initializing base value 
    // to 1, i.e 8^0 
    $base = 1; 
  
    $temp = $num; 
    while ($temp) 
    { 
  
        // Extracting last digit 
        $last_digit = $temp % 10; 
        $temp = $temp / 10; 
  
        // Multiplying last digit 
        // with appropriate base 
        // value and adding it  
        // to dec_value 
        $dec_value += $last_digit * $base; 
  
        $base = $base * 8; 
    } 
  
    return $dec_value; 
} 
  
    // Driver Code 
    $num = 67; 
    echo octalToDecimal($num); 
      
// This code is contributed by anuj_67 
?> 

Output:

This article is contributed by Harsh Agarwal. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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My Personal Notes

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

C/C++

Java

Python3

C#

PHP

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