進数変換

This number base converter switches whole numbers between binary (base 2), octal (base 8), decimal (base 10) and hexadecimal (base 16). Every field is editable, so you can type into any base and read the equivalent in the others instantly.

A number base is just how many distinct digits a system uses before it rolls over to the next position. Decimal uses ten (0 to 9), binary uses two (0 and 1), and hexadecimal uses sixteen, adding a to f for the values ten to fifteen, which is why a single hex digit neatly represents four binary bits.

Conversions use arbitrary-precision integers (BigInt), so even very long values stay exact, without the rounding errors that affect ordinary floating-point numbers once they get large.

Bases come up all over low-level work: hexadecimal for colors, bytes and memory addresses, binary for flags and network masks, and octal for Unix file permissions. Reading the same value across bases makes debugging and bit-twiddling much easier.

A leading minus sign is supported for negatives, spaces are ignored so you can group digits for readability, and an option shows hexadecimal in upper or lower case.

It converts integers only; fractional base conversion is a separate problem and is intentionally left out so the results stay exact. Everything runs in your browser.