Number Base Converter — Free Online Tool
Type one integer, tell us which base it is in, and see it converted to binary, octal, decimal and hexadecimal — with strict digit validation.
How it works
Frequently asked questions
What is the largest number I can convert?
Up to 9,007,199,254,740,991 (Number.MAX_SAFE_INTEGER, or FFFFFFFFFFFF in hex) — the largest integer JavaScript can represent exactly. Larger inputs are rejected rather than silently rounded, so you always get exact digits.
Why does it reject my input?
Each base has strict digit rules: binary accepts only 0 and 1, octal 0–7, decimal 0–9, and hexadecimal 0–9 plus A–F. If you type "2" while Binary is selected, you'll see: "2" is not a valid binary digit. Negative numbers, decimals and fractions are not supported — this converter handles non-negative integers only.
Why non-negative integers only?
Base conversion of negative numbers and fractions needs extra conventions (two's complement, sign-magnitude, fractional digit positions) that differ between contexts. Keeping this tool to non-negative integers means every result is unambiguous and exact — the safest choice for a general-purpose converter.
Binary · Octal · Decimal · Hex · Exact up to 2⁵³−1 · 100% local — your numbers never leave this page.