Developer Resources Updated July 2026

Programming Binary Conversions in Python, Java & C++

Learn how to perform binary-to-decimal and binary-to-octal conversions programmatically in Python and Java using standard built-ins and custom algorithms.

Binary conversions in Python.

Python makes number conversions simple with built-in functions like int(), oct(), and hex().

binary_to_decimal.py 
# Method 1: Using built-in int() with base 2
binary_str = "10101"
decimal_val = int(binary_str, 2)
print(f"Decimal (built-in): {decimal_val}")  # Output: 21

# Method 2: Manual Positional Notation algorithm
def binary_to_decimal_manual(b_str):
    decimal = 0
    for i, digit in enumerate(reversed(b_str)):
        if digit == '1':
            decimal += 2 ** i
    return decimal

print(f"Decimal (manual): {binary_to_decimal_manual('10101')}")  # Output: 21
binary_to_octal.py 
# Convert binary to octal in Python
binary_str = "11010110"
# Step 1: Convert binary to decimal
decimal_val = int(binary_str, 2)
# Step 2: Convert decimal to octal using oct()
octal_str = oct(decimal_val)[2:] # Stripping the '0o' prefix
print(f"Octal: {octal_str}")  # Output: 326

Binary conversions in Java.

In Java, we utilize the static utility methods on the wrapper class Integer, specifically Integer.parseInt() and Integer.toOctalString().

BinaryConversions.java 
public class BinaryConversions {
    public static void main(String[] args) {
        String binaryStr = "10101";

        // 1. Binary to Decimal
        int decimalVal = Integer.parseInt(binaryStr, 2);
        System.out.println("Decimal: " + decimalVal); // Output: 21

        // 2. Binary to Octal
        String octalStr = Integer.toOctalString(decimalVal);
        System.out.println("Octal: " + octalStr); // Output: 25 (octal of 21)
    }
}

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