Last reviewed: 2026 · Updated for 2026

Number Base Converter Guide: Binary, Hex, Decimal & Octal (2026)

Computers think in binary, humans think in decimal, and programmers meet in the middle with hexadecimal. Once you see how these number systems relate, colour codes, memory addresses and bitmasks stop looking cryptic. This guide explains each base and shows you how to convert between them with a free online number base converter.

What a number base actually is

A base is simply how many digits a system uses before it rolls over to the next place. Decimal (base 10) uses 0–9. Binary (base 2) uses only 0 and 1. Octal (base 8) uses 0–7. Hexadecimal (base 16) uses 0–9 then A–F for the values ten to fifteen. The number itself never changes — 255, 0xFF and 0b11111111are the same quantity written three ways.

The four bases you will use

• Binary — how hardware stores everything. Great for understanding bits and flags, painful to read in long strings.
• Decimal — the everyday human base. What most output is finally shown in.
• Hexadecimal — the programmer's shorthand for binary. One hex digit equals four bits, so a byte is two hex digits.
• Octal — three bits per digit. Still seen in Unix file permissions like chmod 755.

Why hex is the programmer's favourite

Hexadecimal exists because raw binary is exhausting to read. A single byte in binary is 11010110; in hex it is just D6. Because four bits map cleanly to one hex digit, you can eyeball byte boundaries instantly. That is why hex shows up in colour codes like #d4af37, memory addresses, hash digests and byte dumps. If you work with colours, our Color Picker shows the same colour in hex and decimal RGB side by side.

How to convert, step by step

1. Open the Number Base Converter.
2. Enter your value and tell the tool which base it is in.
3. Read the equivalent in binary, octal, decimal and hex at once.
4. Copy whichever representation your code or config needs.

Where base conversion helps

Base conversion is a quiet everyday skill. You decode a colour from a design file, read a memory address in a debugger, set Unix permissions with octal, work out a subnet mask in binary, or interpret a byte value from a protocol. Understanding bits also underpins bitwise operations — flags packed into a single integer, for instance. For working with encoded byte data, pair this with our Base64 Encoder and Hash Generator.

Frequently asked questions

Is the converter free? Yes — no sign-up, and it runs in your browser.

What do A–F mean in hex? They are the digits for ten through fifteen, since hex needs sixteen single-character digits.

Can it convert very large numbers? Yes — it handles values well beyond what you can convert comfortably by hand.