Number Tools
4 free tools — precise calculations, instant results.
About Number Tools
Number system converters let you convert between binary, octal, decimal, and hexadecimal number systems. These are the four number bases used in computing, and understanding them is fundamental for programmers, hardware engineers, and computer science students.
The Four Number Systems in Computing
Decimal (base 10) uses digits 0–9 and is the system humans use. Binary (base 2) uses only 0 and 1—this is how all digital computers represent data at the transistor level. Octal (base 8) uses digits 0–7 and was used in early Unix file permissions (e.g., chmod 755). Hexadecimal (base 16) uses 0–9 and A–F, providing a compact representation of binary data widely used in memory addresses, color codes, and encoding.
Binary Numbers: The Foundation of Computing
Every piece of digital information—images, videos, text, programs—is stored as sequences of 0s and 1s. A single binary digit is a bit. 8 bits = 1 byte. 1,024 bytes = 1 kilobyte. Understanding binary helps you grasp bitwise operations, file sizes, network addresses (IP and subnet masks), and color representations (RGB values are 0–255, or 0x00–0xFF in hex).
Roman Numerals: Historical Number System
Roman numerals use letters to represent values: I=1, V=5, X=10, L=50, C=100, D=500, M=1000. The subtractive principle allows smaller values placed before larger ones to be subtracted: IV=4, IX=9, XL=40, XC=90. Roman numerals are still used for clock faces, book chapters, movie sequels, copyright years, and formal outlines.
Frequently Asked Questions
What is the hexadecimal equivalent of 255?
255 in decimal = FF in hexadecimal = 11111111 in binary. This is why maximum RGB color values are 255 (decimal) or FF (hex).
Why do programmers use hexadecimal?
Hexadecimal is a compact representation of binary data. One hex digit represents exactly 4 binary bits (a nibble). Two hex digits represent 8 bits (one byte). Memory addresses, color codes, and character encodings are much more readable in hex than in raw binary.
What is 0xFF in decimal?
0xFF = 255 in decimal. The '0x' prefix indicates a hexadecimal number. F in hex = 15 in decimal. FF = (15 × 16) + 15 = 255.