Twos Complement Calculator

Twos complement is the standard way computers store signed integers. A negative value is the bit pattern you get by adding 2 to the power of the bit width, so -1 in 8 bits is 11111111.

Write the positive value in binary, flip every bit, then add 1. The result is the twos complement form, which this tool computes for you at any width.

An n-bit signed integer runs from minus 2 to the power n minus 1 up to 2 to the power n minus 1, minus 1. For 8 bits that is -128 to 127, so there is one more negative value than positive.

It is the same bit pattern read as a plain unsigned number. For -1 in 8 bits the pattern 11111111 equals 255 when treated as unsigned.

Yes. Enter a bit pattern of the chosen width in the Decode section and the tool reads the top bit to decide the sign, then returns the signed integer it represents. The pattern must be exactly the width you selected.

The menu offers 4, 8, 16, and 32 bits, which cover the common machine word sizes. The underlying engine accepts any width from 1 to 53 bits through the API, but the calculator itself sticks to the four standard choices.

The tool shows an error instead of a wrong answer. If you enter 200 in 8 bits, for example, it tells you the value does not fit and lists the valid range, since 200 is above the 8-bit maximum of 127.

No. Widths are capped at 53 bits because the math runs on JavaScript numbers, which lose exact integer precision above 2 to the power 53. For true 64-bit work use a language with a native 64-bit or BigInt type.

No. Every conversion runs locally in your browser with no network call, so the values you type are never uploaded anywhere.