Free Online Number Base Converter
Type a number in any of the four fields — binary, octal, decimal, or hexadecimal — and the other three update instantly.
Number Base Reference
Binary (base 2)
Uses only digits 0 and 1. The native language of digital hardware; every byte is 8 binary digits. Example: 202₁₀ = 11001010₂.
Octal (base 8)
Uses digits 0–7. Historically used in Unix file permissions (chmod 755) and as a compact alternative to binary — 3 binary digits map to one octal digit.
Decimal (base 10)
The everyday number system using digits 0–9. The default for humans and most high-level programming languages.
Hexadecimal (base 16)
Uses digits 0–9 and letters A–F. One hex digit represents exactly 4 binary bits, making it compact for memory addresses, colour codes (#FF6347), and byte values.
Frequently Asked Questions
Type the binary number into the Binary field — the Decimal, Octal, and Hexadecimal fields update instantly. There's no need to work out the place-value math (128s, 64s, 32s…) by hand.
No, it works with positive whole numbers only. For negative values in a programming context, remember that most languages represent negative integers using two's complement in binary rather than a simple minus sign.
Hex needs 16 distinct digits per place (0-15), but our number system only has 10 digit symbols (0-9). Letters A-F fill in for values 10 through 15, so a single hex digit can represent any value from 0 to 15 — exactly what 4 binary bits can hold.
Its most visible modern use is Unix/Linux file permissions (e.g. chmod 755) — each digit maps to a permission triplet (read/write/execute) for owner, group, and others. Historically it was also common in early computing when 12-bit and 36-bit word sizes made octal a cleaner fit than hex.
It's completely free with no limits, and nothing is sent anywhere — conversion happens entirely in your browser using JavaScript.