Program for Hexadecimal to Decimal

14 Sep, 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
Chapters
descriptions off, selected
captions settings, opens captions settings dialog
captions off, selected
English
This is a modal window.
Beginning of dialog window. Escape will cancel and close the window.
End of dialog window.
The below diagram explains how to convert a hexadecimal number (1AB) to an equivalent decimal value:  
Below is the implementation of the above idea. 
C++
Java
Python3
C#
PHP
Javascript
// C++ program to convert hexadecimal to decimal#include <bits/stdc++.h>using namespace std; // Function to convert hexadecimal to decimal int hexadecimalToDecimal(string hexVal){    int len = hexVal.size();     // 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 += (int(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 += (int(hexVal[i]) - 55) * base;             // incrementing base by power            base = base * 16;        }    }    return dec_val;} // driver programint main(){    string hexNum = "1A";    cout << (hexadecimalToDecimal(hexNum));     // This code is contributed by rakeshsahni     return 0;}
// Java program to convert hexadecimal to decimalimport 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 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 codeif __name__ == '__main__':     hexnum = '1A'     print(hexadecimalToDecimal(hexnum)) # This code is contributed by virusbuddah_
// C# program to convert// hexadecimal to decimalusing 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 program to convert// hexadecimal to decimal // Function to convert// hexadecimal to decimalfunction 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?>
<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 programvar hexNum = "1A";document.write(hexadecimalToDecimal(hexNum)); // This code is contributed by 29AjayKumar</script>
26
Using predefined function
C++
Java
Python3
C#
Javascript
// C++ program to convert octal to decimal#include <bits/stdc++.h>using namespace std;int HexToDec(string n) { return stoi(n, 0, 16); } int main(){    string n = "1A";    cout << HexToDec(n);     return 0;}     // This code is contributed by rakeshsahni
// 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));    }}
# Python program to convert hexadecimal to decimaldef HexToDec(n):    return int(n, 16); if __name__ == '__main__':    n = "1A";    print(HexToDec(n));     # This code is contributed by 29AjayKumar
// 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
<script>// javascript program to convert octal to decimalfunction HexToDec(n)    {        return parseInt(n, 16);    }     var n = "1A";document.write(HexToDec(n));// This code is contributed by 29AjayKumar</script>
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 review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above. 
Mithun Kumar
soumya7
virusbuddha
le0
29AjayKumar
amit143katiyar
rakeshsahni
base-conversion
Computer Organization & Architecture
Digital Electronics & Logic Design
GATE CS
Writing code in comment?
Please use ide.geeksforgeeks.org,
generate link and share the link here.