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Ones Complement
Work out the ones complement, the twos complement and the signed reading of a binary value at any bit width.
Complement a binary value
Value: —
Unsigned decimal: —
Ones complement: —
Twos complement: —
Signed value: —
How to use the Ones Complement
- Choose the bit width you are working at.
- Type the binary value, padded or unpadded.
- Read the ones complement, twos complement and signed value.
Features
- Ones and twos complement of any bit width
- Values padded or truncated to the chosen width
- Signed interpretation using the twos complement rule
- Wrap detection when the twos complement overflows
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Frequently Asked Questions
Common questions about the free online ones complement.
The ones complement flips every bit of a value, so 00101011 becomes 11010100 at the same bit
width.
The twos complement is the ones complement plus one, and it is how computers store negative
whole numbers.
Adding one makes the pattern of zero unique and makes binary addition and subtraction work
with the same hardware.
If the leading bit is one the number is negative. Take the twos complement of the pattern and
put a minus sign in front.
It does. The complement is always taken across the whole chosen width, so an 8-bit and a
16-bit answer will differ.
Values are padded with leading zeros when short and only the lowest bits are kept when longer
than the width.
Yes. Complementing an all zeros pattern wraps past the width, and the tool reports when that
happens.
In ones complement an all ones pattern means negative zero, which is one reason twos
complement took over.
Yes. The ones complement is exactly the bitwise NOT of the value across the selected width.
No. All of the bit maths happens locally in your browser.
Last updated: October 10, 2026