Decimal to two's complement converter
Two's complement is how processors store negative integers. Pick a bit width to see the value as it sits in memory.
Loading the tool…
Processing and privacy: The result is calculated inside your browser and your data is not sent to any server.
How to use it
- Enter decimal integer and bit width.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
For a positive number: its binary value padded with zeros to the width. For a negative one: write its absolute value in binary, invert every bit and add 1, which equals 2 to the power n plus the number.
Example
Inputs: Decimal integer = -42, Bit width = 8-bit. Result: Two's complement: 11010110; Range at this width: -128 to 127.
-42
11010110
Limits and caveats
- Whole numbers only; fractional values need a floating-point format.
- A number outside the chosen width is rejected rather than wrapped.
Questions about this tool
How is -42 written in 8-bit two's complement?
42 = 00101010. Invert the bits to get 11010101, then add 1 to get 11010110, which is D6.
What range fits in 8 bits?
-128 to 127. In general, from minus 2 to the power (n-1) up to 2 to the power (n-1) minus 1.
Why do computers use two's complement?
Addition and subtraction use the same circuit for positive and negative numbers, and zero has only one form.