Number Base Converter

How to use the number base converter

1. Type your number and say which base it is written in.
2. Read the other bases, or set any base up to 36.
3. Copy whichever form you need.

About this tool

Every base is shown at once, because converting usually means checking one against another — a hex colour against its decimal channels, a permission mask against its binary bits.

The arithmetic uses arbitrary-precision integers rather than ordinary JavaScript numbers. That matters beyond about 9 quadrillion, where a normal number silently loses its least significant digits: convert a 20-digit hex value the usual way and the answer is quietly wrong. Here it stays exact.

The width readouts show how many bits and bytes a value needs, which is the practical question when a number has to fit a field.

Common uses

• Converting a hex colour or byte value to decimal.
• Reading a binary flag or permission mask.
• Checking whether a value fits in 8, 16 or 32 bits.

Frequently asked questions

Why do hex numbers start with 0x?

It is a prefix used in most programming languages to mark the base — 0b for binary, 0o for octal, 0x for hex. This tool accepts them and shows the prefixed form.

Are very large numbers exact?

Yes. Conversion uses arbitrary-precision integers, so values beyond JavaScript's safe range keep every digit.