Free Online Number Base Converter
Convert numbers between binary, octal, decimal, and hexadecimal instantly — free online tool, 100% client-side, supports up to 64-bit values.
100% Client-Side · Your data never leaves your browserHow to Use Number Base Converter
Select the From Base that matches your input: Decimal, Binary, Octal, or Hexadecimal. Type your value in the input field (spaces and underscores are ignored, so 1111 0000 and 0xFF_AA both work).
Click Convert to see all four representations at once. Binary output is grouped into nibbles (4 bits) for readability, and hex output is grouped into bytes.
Click the copy icon next to any result to copy the raw value without spaces.
Frequently Asked Questions
What is a number base?
A number base (or radix) defines how many distinct digits a positional numeral system uses. Decimal (base 10) uses digits 0–9. Binary (base 2) uses 0 and 1. Octal (base 8) uses 0–7. Hexadecimal (base 16) uses 0–9 plus A–F.
Why do programmers use hexadecimal?
Hexadecimal is compact: one hex digit represents exactly 4 binary bits, and two hex digits represent one byte. This makes memory addresses, color codes, byte arrays, and bitmasks far more readable than long binary strings.
How do I convert decimal 255 to binary?
Divide 255 by 2 repeatedly and note the remainders from bottom to top: 255 = 11111111 in binary. In hexadecimal it is FF, and in octal it is 377. This tool computes all conversions instantly.
What is the maximum value this tool supports?
The converter supports values up to 18,446,744,073,709,551,615 — the maximum 64-bit unsigned integer (0xFFFFFFFFFFFFFFFF in hex). Values beyond this range are rejected.
How are hex color codes related to base conversion?
CSS hex colors like #FF8000 encode three bytes: red (FF = 255), green (80 = 128), blue (00 = 0). Converting each two-character hex pair to decimal gives the RGB channel values.