What is two's complement?

Two's complement is the standard way computers store signed integers. A negative value −n at width w is stored as 2^w − n, so the most significant bit acts as the sign bit and addition works without special cases.

What happens if my number is out of range?

Each width has a fixed signed range (for 8-bit it is −128 to 127). If you enter a value outside the range the tool warns you and shows the wrapped-around encoding.

Is anything sent to a server?

No — the conversion happens entirely in your browser and nothing is uploaded.

Two's Complement Calculator

Signed decimal to two's complement binary and hex.

Two’s complement calculator

See how a signed decimal integer is stored in two’s complement form at 8, 16, 32 or 64 bits. The tool shows the binary pattern, the hexadecimal value, and both the unsigned and signed interpretations of the same bits.

Two’s complement is how nearly every modern CPU represents negative integers: −n is stored as 2^w − n for a width of w bits, which lets addition and subtraction work with a single circuit. Everything runs locally in your browser.