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Program for Hexadecimal to Decimal

  • Difficulty Level : Easy
  • Last Updated : 19 May, 2021

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

Examples:  

Input : 67
Output: 103

Input : 512
Output: 1298

Input : 123
Output: 291

We know that 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 a given hexadecimal number starting from the rightmost 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. In 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



The below diagram explains how to convert a hexadecimal number (1AB) to an equivalent decimal value:  

Below is the implementation of the above idea. 

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));
    }
}

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
?>

Javascript




<script>
// javascript program to convert hexadecimal to decimal
   // Function to convert hexadecimal to decimal
 
function hexadecimalToDecimal(hexVal)
{
    var len = hexVal.length;
 
    // Initializing base value to 1, i.e 16^0
    var base = 1;
 
    var dec_val = 0;
 
    // Extracting characters as digits from last
    // character
    for (var 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).charCodeAt(0) - 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).charCodeAt(0) - 55) * base;
 
            // incrementing base by power
            base = base * 16;
        }
    }
    return dec_val;
}
 
// driver program
var hexNum = "1A";
document.write(hexadecimalToDecimal(hexNum));
 
// This code is contributed by 29AjayKumar
</script>
Output
26

Using predefined function

Java




// Java program to convert hexadecimal to decimal
 
import java.io.*;
 
class GFG {
    public static int HexToDec(String n)
    {
        return Integer.parseInt(n, 16);
    }
    public static void main(String[] args)
    {
        String n = "1A";
        System.out.println(HexToDec(n));
    }
}

Python3




# Python program to convert hexadecimal to decimal
def HexToDec(n):
    return int(n, 16);
 
if __name__ == '__main__':
    n = "1A";
    print(HexToDec(n));
     
# This code is contributed by 29AjayKumar

C#




// C# program to convert hexadecimal to decimal
 
using System;
 
public class GFG {
    public static int HexToDec(String n)
    {
        return Convert.ToInt32(n, 16);
    }
    public static void Main(String[] args)
    {
        String n = "1A";
        Console.WriteLine(HexToDec(n));
    }
}
 
// This code is contributed by Amit Katiyar

Javascript




<script>
// javascript program to convert octal to decimal
function HexToDec(n)
    {
        return parseInt(n, 16);
    }
     
var n = "1A";
document.write(HexToDec(n));
// This code is contributed by 29AjayKumar
</script>
Output
26

This article is contributed by Harsh Agarwal. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.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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