Number Base Converter
Convert numbers between binary, octal, decimal and hexadecimal — arbitrary size, entirely in your browser.
Processed entirely in your browser — nothing you enter here is ever uploaded.
Result
About this tool
Binary for bit masks, hexadecimal for colors and memory addresses, octal for Unix permissions, decimal for everything human — sooner or later every developer, student or electronics hobbyist needs to move a number from one base to another. This converter does it in one click: pick the source base, pick the target base, type the value.
Unlike calculators built on ordinary floating-point numbers, this tool uses BigInt arithmetic, so a 256-bit hash, a long IPv6-sized value or a thousand-digit exercise from a textbook all convert exactly, with no rounding and no overflow. Every digit is validated against the source base first, so a stray 8 in an octal value or a g in hex is reported instead of silently producing garbage.
The result panel shows more than the single answer: alongside the converted value you get the same number written in binary, octal, decimal and hexadecimal, which is exactly what you want when debugging bitwise code or checking a checksum by eye.
Everything runs locally in your browser — no server round-trip, no logs, no limits. Preset pages for the popular pairs (binary to decimal, decimal to hex and friends) open the tool with both bases already selected.
Example. Decimal 255 converts to hexadecimal ff, binary 11111111, and octal 377.
Limit. The only bases are 2, 8, 10, and 16, and a digit that does not belong in the source base is rejected.