Number base converter
Convert between binary, octal, decimal, hex, ASCII bytes, and arbitrary bases 2–36 with BigInt.
Runs in this tab. The file stays here.
Uses BigInt — large hex values stay exact. Type in any field to update the rest.
This runs in your browser. Nothing is uploaded.
About Number base converter
Convert between binary, octal, decimal, hexadecimal, ASCII bytes, and arbitrary bases 2–36 using BigInt so large values stay exact.
Online base converters that use plain JavaScript numbers silently corrupt anything past 2^53. This page uses BigInt for the number mode so a long hex string still round-trips.
Type in any of the four main fields and the others update live. Invalid digits for that base are filtered as you type. Arbitrary base 2–36 covers the rarer “convert to base 36” requests.
ASCII / bytes mode is a different job: each character becomes a byte value shown space-separated in the chosen base (Hi → 48 69 in hex). Useful for short byte strings, not a single integer.
How to use Number base converter
- 1Pick Number or ASCII / bytes mode.
- 2Type in binary, octal, decimal, or hex — or paste text in ASCII mode.
- 3Copy the field you need; use the arbitrary-base row when 2–36 matters.
What it won't do
- Non-negative integers only; no floating-point bases.
- ASCII mode is UTF-8 bytes, not code points outside the encoder's mapping.
Common questions
Why BigInt instead of Number?
Number loses integer precision above 2^53−1. BigInt keeps arbitrary-size integers exact for conversion.
Does ASCII mode convert the whole string to one number?
No. It maps each UTF-8 byte to a value in the active base, space-separated.
Are negative numbers supported?
Not in this version. Unsigned non-negative integers only.
Related tools
Why this one doesn't upload your file
There is no server to upload to. This page is a static file, and the work happens in your browser using the same graphics and WebAssembly code that renders every other site you visit. Your file is read from disk into memory, processed, and handed back as a download. Once the page has loaded you can disconnect from the network entirely and it keeps working. The longer explanation