Free Number Base Converter Online — Binary, Hex, Octal, Decimal

Convert numbers between binary, octal, decimal, and hexadecimal instantly with this free online base converter. Type a value in any field and the others update in real time — essential for programmers, students, and anyone working with low-level data. Runs entirely in your browser.

How to Use This Base Converter

1. Type a number into any of the four fields
2. The other bases update instantly
3. Invalid input for a base is flagged automatically

Understanding Number Bases

A number base (or radix) defines how many unique digits represent values. Computers use binary internally; programmers often use hex and octal as compact shorthand.

• Decimal (base 10) — digits 0–9, the everyday number system
• Binary (base 2) — digits 0–1, how computers store all data
• Hexadecimal (base 16) — digits 0–9 and A–F, used for colors, memory addresses, and byte values
• Octal (base 8) — digits 0–7, used in Unix file permissions

Common Conversions

• 255 decimal = 11111111 binary = FF hex = 377 octal
• 16 decimal = 10000 binary = 10 hex = 20 octal
• 8 decimal = 1000 binary = 8 hex = 10 octal

Where You’ll Use Each Base

• Hex — CSS colors (#FF5733), memory addresses, MAC addresses, byte dumps
• Binary — bitwise operations, flags, low-level hardware programming
• Octal — Unix/Linux file permissions (chmod 755)

Privacy

All conversions run in your browser using JavaScript’s built-in number parsing. Nothing is sent to any server.

Recommended Reading

Go deeper into how computers represent and process numbers:

• Code: The Hidden Language of Computer Hardware — essential reading for how computers represent numbers
• Computer Systems: A Programmer’s Perspective — essential reading for binary and data representation
• But How Do It Know? — essential reading for computer fundamentals

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