Edit any field — binary, octal, decimal, or hexadecimal — the others update live.
How it works
Typing in any field runs JavaScript's parseInt() with that field's base to get a plain number, then re-renders the other three fields with toString(2), toString(8), toString(16), and so on - so all four stay in sync without a page reload, and invalid input (like an 8 in a binary field) is caught before it can corrupt the other fields.
FAQ
Why does it reject negative numbers?
parseInt in a given base can't cleanly represent negative numbers the way this converter displays binary, octal, and hex, so any negative result shows an error instead of an incorrect guess.
Does it support numbers larger than a 32-bit integer?
Only up to JavaScript's safe integer limit (2^53-1) - beyond that, rounding in toString() will make the other bases display incorrectly, so this isn't a general-purpose bignum converter.
Free, unlimited, no account. If this saved you a paid tool, a small thanks is appreciated.