Number Base Converter

What is a number base?

A number's "base" (or radix) is how many distinct digits its number system uses before it carries over to the next place value — base 10 (decimal) is the everyday system with digits 0–9, base 2 (binary) is what computers use internally with just 0 and 1, base 8 (octal) and base 16 (hexadecimal) are common shorthand for binary data in programming, and any base up to 36 can be built using digits 0–9 plus letters a–z for the extra digit values.

This converter shows binary, octal, decimal, hexadecimal, and a custom radix of your choosing all at once — and every one of them is editable. Type into any field and the rest update instantly, so there's no need to pick a "from" base first; whichever field you type in becomes the source.

How to use it

How the conversion works

Whichever field you edit is parsed digit by digit in that field's base, treating letters a–z as the digit values 10 through 35, and reconstructed as an arbitrary-precision integer rather than a standard JavaScript number — which matters because regular numbers lose precision above 2^53, while this approach stays exact no matter how long the input is. That value is then re-expressed in every other base — including the custom radix — and those fields update immediately, while the field you're actively typing in is left untouched so your cursor position isn't disturbed.

Features & benefits

Why this runs entirely in your browser

Every conversion runs in JavaScript locally in the tab using arbitrary-precision integer math, which means it keeps working offline once the page has loaded and nothing typed into it is ever sent to a server.

Common uses

Converting a hex color or memory address to binary to understand its bit pattern, checking an octal file permission value in decimal, converting a base-36 short ID back to a plain integer, or working through a computer science exercise on number systems.