Number Base Converter Online - Binary Hex Decimal

Convert between binary, octal, decimal, hex. Fast, secure, and completely free. All processing happens in your browser — no data is sent to any server.

What is a Number Base Converter?

A Number Base Converter translates a numeric value between binary (base 2), octal (base 8), decimal (base 10), and hexadecimal (base 16) — or any custom base you specify — representing the exact same underlying quantity in a different positional numbering system. Programmers work across these bases constantly: hex for representing bytes and color values compactly, binary for understanding bitwise operations and flags, and octal for legacy Unix file permissions, and converting between them by hand for anything beyond small numbers is slow and error-prone.

How to Use Number Base Converter

  1. Enter a number in any supported base (binary, octal, decimal, or hexadecimal)
  2. The equivalent value in all other bases updates automatically
  3. Select a custom base if you need a conversion beyond the four common ones
  4. Copy the specific base representation you need for your code or documentation
  5. Verify a manually calculated conversion before using it in your work

Key Features

Why Use Number Base Converter?

Reading a hex color code, decoding a Unix file permission octal value (like chmod 755), or understanding a bitmask flag value in binary all require moving fluently between number bases, and while experienced developers can do small conversions mentally, larger numbers or unusual bases are easy to get wrong by hand. Converting instantly removes that friction when you're debugging a binary flag, reading a memory address in hex, or double-checking a permission value before running a chmod command.

Common Use Cases

Frequently Asked Questions

Why does chmod use octal numbers like 755 for file permissions?

Each octal digit conveniently represents exactly 3 bits, which maps perfectly onto the 3 permission flags (read, write, execute) for each of the 3 permission groups (owner, group, others) in Unix — this is why octal remains standard for representing file permissions.

How do I convert a negative number between bases?

Negative numbers are typically handled either with a minus sign prefix on the magnitude, or via two's complement representation in binary/hex for a specific bit width — check which convention your specific use case (like a programming language's integer type) expects.

Can it handle numbers larger than a standard 32-bit or 64-bit integer?

Yes, arbitrary-precision conversion supports numbers well beyond typical integer size limits, which is useful for cryptographic values or very large identifiers.

What does it mean to convert to a 'custom' base, like base 36?

Base 36 uses digits 0-9 plus letters A-Z to represent values compactly, which is a common technique for generating short, URL-friendly identifiers from larger numeric IDs.

Why do hex numbers use letters A through F?

Hexadecimal (base 16) needs 16 distinct digit symbols; after 0-9, it continues with A-F to represent the values 10 through 15 in a single character.

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