Binary to decimal using C#

Converting binary numbers to decimal is a fundamental operation in programming. In C#, you can convert binary to decimal using manual calculation methods or built-in functions. The binary number system uses base 2, where each digit position represents a power of 2.

How Binary to Decimal Conversion Works

Binary to decimal conversion follows a simple mathematical principle. Each binary digit (bit) is multiplied by the corresponding power of 2, starting from 2? for the rightmost digit −

Using Manual Calculation Method

This approach extracts each binary digit and multiplies it by the corresponding power of 2 −

using System;

class BinaryToDecimal {
    static void Main(string[] args) {
        int val = 1010, myBinary, remainder;
        int myDecimal = 0, baseVal = 1;
        myBinary = val;
        
        while (val > 0) {
            remainder = val % 10;
            myDecimal = myDecimal + remainder * baseVal;
            val = val / 10;
            baseVal = baseVal * 2;
        }
        
        Console.WriteLine("Binary Number: " + myBinary);
        Console.WriteLine("Converted to Decimal: " + myDecimal);
    }
}

The output of the above code is −

Binary Number: 1010
Converted to Decimal: 10

Using Convert.ToInt32() Method

C# provides a built-in method to convert binary strings to decimal numbers −

using System;

class BinaryConverter {
    static void Main(string[] args) {
        string binaryString = "1010";
        int decimalValue = Convert.ToInt32(binaryString, 2);
        
        Console.WriteLine("Binary: " + binaryString);
        Console.WriteLine("Decimal: " + decimalValue);
        
        // Multiple examples
        string[] binaryNumbers = {"1100", "1111", "10101"};
        
        foreach (string binary in binaryNumbers) {
            int result = Convert.ToInt32(binary, 2);
            Console.WriteLine($"Binary {binary} = Decimal {result}");
        }
    }
}

The output of the above code is −

Binary: 1010
Decimal: 10
Binary 1100 = Decimal 12
Binary 1111 = Decimal 15
Binary 10101 = Decimal 21

Using Custom Method with Math.Pow

This approach uses mathematical power calculation for clearer understanding −

using System;

class BinaryDecimalConverter {
    static int BinaryToDecimal(string binary) {
        int decimalValue = 0;
        int power = 0;
        
        // Process from right to left
        for (int i = binary.Length - 1; i >= 0; i--) {
            if (binary[i] == '1') {
                decimalValue += (int)Math.Pow(2, power);
            }
            power++;
        }
        
        return decimalValue;
    }
    
    static void Main(string[] args) {
        string[] testBinaries = {"1010", "1100", "11111", "10000"};
        
        foreach (string binary in testBinaries) {
            int decimal_result = BinaryToDecimal(binary);
            Console.WriteLine($"Binary {binary} converts to Decimal {decimal_result}");
        }
    }
}

The output of the above code is −

Binary 1010 converts to Decimal 10
Binary 1100 converts to Decimal 12
Binary 11111 converts to Decimal 31
Binary 10000 converts to Decimal 16

Comparison of Methods

Conclusion

Converting binary to decimal in C# can be accomplished through manual calculation, built-in methods like Convert.ToInt32(), or custom mathematical approaches. The built-in method is most efficient for production code, while manual methods help understand the underlying conversion process.