Program for Hexadecimal to Decimal

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

Examples:

Input : 67
Output : 103

Input : 512
Output : 1298

Input: 123
Output: 291

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

We know that in hexadecimal number uses 16 symbols {0, 1, 2, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F} to represent all numbers. Here, (A, B, C, D, E, F) represents (10, 11, 12, 13, 14, 15).
The idea is to extract the digits of given hexadecimal number starting from right most digit and keep a variable dec_value. At the time of extracting digits from the hexadecimal number, multiply the digit with the proper base (Power of 16) 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 hexadecimal number is 1A.
dec_value = 1*(16^1) + 10*(16^0) = 26

Below diagram explains how to convert hexadecimal number ( 1AB ) to equivalent decimal value:

Below is the implementation of above idea.

C/C++

// C++ program to convert hexadecimal to decimal 
#include<iostream> 
#include<string.h> 
using namespace std; 
  
// Function to convert hexadecimal to decimal 
int hexadecimalToDecimal(char hexVal[]) 
{    
    int len = strlen(hexVal); 
      
    // Initializing base value to 1, i.e 16^0 
    int base = 1; 
      
    int dec_val = 0; 
      
    // Extracting characters as digits from last character 
    for (int i=len-1; i>=0; i--) 
    {    
        // if character lies in '0'-'9', converting  
        // it to integral 0-9 by subtracting 48 from 
        // ASCII value. 
        if (hexVal[i]>='0' && hexVal[i]<='9') 
        { 
            dec_val += (hexVal[i] - 48)*base; 
                  
            // incrementing base by power 
            base = base * 16; 
        } 
  
        // if character lies in 'A'-'F' , converting  
        // it to integral 10 - 15 by subtracting 55  
        // from ASCII value 
        else if (hexVal[i]>='A' && hexVal[i]<='F') 
        { 
            dec_val += (hexVal[i] - 55)*base; 
          
            // incrementing base by power 
            base = base*16; 
        } 
    } 
      
    return dec_val; 
} 
  
// Driver program to test above function 
int main() 
{ 
    char hexNum[] = "1A";     
    cout << hexadecimalToDecimal(hexNum) << endl; 
    return 0; 
} 

Java

// Java program to convert hexadecimal to decimal 
import java.io.*; 
  
class GFG  
{ 
    // Function to convert hexadecimal to decimal 
    static int hexadecimalToDecimal(String hexVal) 
    {    
        int len = hexVal.length(); 
       
        // Initializing base value to 1, i.e 16^0 
        int base = 1; 
       
        int dec_val = 0; 
       
        // Extracting characters as digits from last character 
        for (int i=len-1; i>=0; i--) 
        {    
            // if character lies in '0'-'9', converting  
            // it to integral 0-9 by subtracting 48 from 
            // ASCII value 
            if (hexVal.charAt(i) >= '0' && hexVal.charAt(i) <= '9') 
            { 
                dec_val += (hexVal.charAt(i) - 48)*base; 
                   
                // incrementing base by power 
                base = base * 16; 
            } 
   
            // if character lies in 'A'-'F' , converting  
            // it to integral 10 - 15 by subtracting 55  
            // from ASCII value 
            else if (hexVal.charAt(i) >= 'A' && hexVal.charAt(i) <= 'F') 
            { 
                dec_val += (hexVal.charAt(i) - 55)*base; 
           
                // incrementing base by power 
                base = base*16; 
            } 
        } 
        return dec_val; 
    } 
      
    // driver program 
    public static void main (String[] args)  
    { 
        String hexNum = "1A";     
        System.out.println(hexadecimalToDecimal(hexNum)); 
    } 
} 
  
// Contributed by Pramod Kumar 

Python3

# Python3 program to convert  
# hexadecimal to decimal 
  
# Function to convert hexadecimal 
# to decimal 
def hexadecimalToDecimal(hexval): 
      
    # Finding length 
    length = len(hexval) 
      
    # Initialize base value to 1, 
    # i.e. 16*0 
    base = 1
    dec_val = 0
      
    # Extracting characters as digits 
    # from last character 
    for i in range(length - 1, -1, -1): 
          
        # If character lies in '0'-'9',  
        # converting it to integral 0-9   
        # by subtracting 48 from ASCII value 
        if hexval[i] >= '0' and hexval[i] <= '9': 
            dec_val += (ord(hexval[i]) - 48) * base 
              
            # Incrementing base by power 
            base = base * 16
          
        # If character lies in 'A'-'F',converting 
        # it to integral 10-15 by subtracting 55 
        # from ASCII value 
        elif hexval[i] >= 'A' and hexval[i] <= 'F': 
            dec_val += (ord(hexval[i]) - 55) * base 
              
            # Incrementing base by power 
            base = base * 16
              
    return dec_val 
  
# Driver code 
if __name__ == '__main__': 
      
    hexnum = '1A'
      
    print(hexadecimalToDecimal(hexnum)) 
  
# This code is contributed by virusbuddah_ 

C#

// C# program to convert  
// hexadecimal to decimal 
using System; 
  
class GFG  
{ 
// Function to convert  
// hexadecimal to decimal 
static int hexadecimalToDecimal(String hexVal) 
{  
    int len = hexVal.Length; 
  
    // Initializing base1 value  
    // to 1, i.e 16^0 
    int base1 = 1; 
  
    int dec_val = 0; 
  
    // Extracting characters as 
    // digits from last character 
    for (int i = len - 1; i >= 0; i--) 
    {  
        // if character lies in '0'-'9',  
        // converting it to integral 0-9  
        // by subtracting 48 from ASCII value 
        if (hexVal[i] >= '0' &&  
            hexVal[i] <= '9') 
        { 
            dec_val += (hexVal[i] - 48) * base1; 
              
            // incrementing base1 by power 
            base1 = base1 * 16; 
        } 
  
        // if character lies in 'A'-'F' ,  
        // converting it to integral  
        // 10 - 15 by subtracting 55  
        // from ASCII value 
        else if (hexVal[i] >= 'A' &&  
                 hexVal[i] <= 'F') 
        { 
            dec_val += (hexVal[i] - 55) * base1; 
      
            // incrementing base1 by power 
            base1 = base1 * 16; 
        } 
    } 
    return dec_val; 
} 
  
// Driver Code 
static void Main()  
{ 
    String hexNum = "1A";  
    Console.WriteLine(hexadecimalToDecimal(hexNum)); 
} 
} 
  
// This code is contributed by mits 

PHP

<?php 
// PHP program to convert  
// hexadecimal to decimal 
  
// Function to convert 
// hexadecimal to decimal 
function hexadecimalToDecimal($hexVal) 
{  
    $len = strlen($hexVal); 
      
    // Initializing base value  
    // to 1, i.e 16^0 
    $base = 1; 
      
    $dec_val = 0; 
      
    // Extracting characters as  
    // digits from last character 
    for ($i = $len - 1; $i >= 0; $i--) 
    {  
        // if character lies in '0'-'9',  
        // converting it to integral 0-9  
        // by subtracting 48 from ASCII value. 
        if ($hexVal[$i] >= '0' &&  
            $hexVal[$i] <= '9') 
        { 
            $dec_val += (ord($hexVal[$i]) - 48) *  
                                         $base; 
                  
            // incrementing base by power 
            $base = $base * 16; 
        } 
  
        // if character lies in 'A'-'F' ,   
        // converting it to integral  
        // 10 - 15 by subtracting 55  
        // from ASCII value 
        else if ($hexVal[$i] >= 'A' &&  
                 $hexVal[$i] <= 'F') 
        { 
            $dec_val += (ord($hexVal[$i]) - 55) *  
                                         $base; 
          
            // incrementing base by power 
            $base = $base * 16; 
        } 
    } 
      
    return $dec_val; 
} 
  
// Driver Code 
$hexNum = "1A";  
echo hexadecimalToDecimal($hexNum); 
  
// This code is contributed by mits 
?> 

Output:

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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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