What is -6 in 8-bit two’s complement?

The bits are 11111010. The same bits read as 250 without a sign.

How do I convert the bits back to a decimal value?

Invert every bit, add 1, then read the result as a magnitude with a minus sign in front.

Every bit has the value 1. In 8 bits that is 0xFF, and in 32 bits it is 0xFFFFFFFF.

Two’s complement holds a negative value in a fixed number of bits.

To get the bits, invert every bit of the magnitude and add 1.

The value -6 in 8 bits gives 11111010, which reads as 250 without a sign.

The bits 11111010, which give -6. Edit the expression or select a bit to flip it.

Expression

-6

value · 8 bits · signed

Read the bits as

Bit width

Read the bits in the editor as a value: The steps follow the value above.

A few values in 8-bit two’s complement
Signed value	Bits	Unsigned reading	Hex
-1	11111111	255	0xFF
-6	11111010	250	0xFA
-128	10000000	128	0x80
0	00000000	0	0x00
127	01111111	127	0x7F

A sensor that reports a temperature below zero sends these bits.

A register field that holds an offset needs the same form.

A value that reads as a large positive number is often a negative value with the wrong sign mode.

A change of the sign mode does not change the bits. The same bits give a different reading.
The top bit is not a minus sign. The top bit carries part of the value.
A wider bit width needs the sign copied into every new bit, which the name sign extension covers.
The range is not symmetric, because zero takes one of the positive codes.

The full editor holds many values, evaluates expressions across them, and reads live values from a serial port.

What is -6 in 8-bit two’s complement?: The bits are 11111010. The same bits read as 250 without a sign.
How do I convert the bits back to a decimal value?: Invert every bit, add 1, then read the result as a magnitude with a minus sign in front.
What is -1 in any width?: Every bit has the value 1. In 8 bits that is 0xFF, and in 32 bits it is 0xFFFFFFFF.