Decimal, hex, binary and octal converter

The formula

unsigned = Σ bit[i] · 2^i signed (two’s complement) = unsigned − 2^bits, if the top bit is set

When to use it

Reading a register dump, building a bitmask, checking what a negative value looks like in hex, or just converting a value while reverse-engineering a protocol. The bit grid is the fastest way to see which flags are set without doing the arithmetic yourself.

Pitfalls

• A value typed as unsigned can be out of range for the same width signed, and the other way around — the field goes red instead of silently wrapping.
• 0xFF is 255 unsigned but −1 signed at 8 bits; the same bit pattern means different numbers depending on how the code reads it.
• 64-bit values exceed what JavaScript’s plain numbers can represent exactly past 2^53 — this tool uses BigInt throughout so the full 64-bit range stays exact.
• The ASCII column only means something for the low byte; it is a convenience for text bytes, not a property of the whole value.

Related note