Number Base Converter

What is Number Base Converter?

Number Base Converter is a free online tool for converting numbers between binary, octal, decimal, hexadecimal and any other base from 2 to 36. Most converters quietly fall apart beyond 2^53 because they lean on floating-point math; this one accumulates with arbitrary-precision integers, so a 128-bit hash or a giant bitmask converts exactly. Binary, octal, decimal and hex results are always shown, and an optional custom base adds a fifth.

Features

• Any base 2-36 — digits 0-9 then a-z, case-insensitive, with per-digit validation that names the offending character
• Arbitrary precision — BigInt accumulation means no rounding, ever, no matter how long the input
• Prefix-aware — 0x, 0b and 0o prefixes are accepted when they match the selected From base, and rejected with a clear message when they don't (0x1A is still a perfectly valid base-36 number)
• Negative values — a leading minus converts sign-magnitude style: the sign is carried to every output, no two's-complement surprises
• Uppercase hex — hexadecimal output uses A-F uppercase for readability

How to use

Type or paste the value, pick the base it is written in (2-36; binary, octal, decimal and hex sit at the top of the list), and read the four conversions instantly — each row has its own copy button. Need base 7 or base 32? Fill in To base (custom) and a fifth row appears.

Privacy

Conversion runs locally in the browser UI. Values you convert on the page are not uploaded or logged.