Program for Hexadecimal to Decimal (original) (raw)

Last Updated : 3 Apr, 2025

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

Hexadecimal Number

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*(161) + 10*(160) = 26

Decimal Number

The number which can be represented using the numbers in the range of (0-9) are termed as decimal number which has the base 10 to it.

For example, The number 123 is a decimal number where:

• 1 represents 100 (10²),
• 2 represents 20 (10¹),
• 3 represents 3 (10⁰).

Thus, 123 = 1×100 + 2×10 + 3×1.

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++ `

// 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 program int main() { string hexNum = "1A"; cout << (hexadecimalToDecimal(hexNum));

// This code is contributed by rakeshsahni

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));
}

}

Python

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

JavaScript

PHP

`

**Time Complexity: O(N), where N is the number of digits in the given hexadecimal number.

**Space Complexity: O(1).

**Using predefined function

C++ `

// 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

// 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

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

`

**Time complexity: O(1) - the conversion of hexadecimal to decimal is done in constant time using the stoi function.
**Auxiliary Space: O(1) - the only space used is for the string n and the returned integer value, which are constant in size regardless of the input value.