Two's complement of 127
The 8-bit two's complement of 127 is 10000001, the bit pattern that represents -127 (minus 127). Written as a signed 8-bit number, 127 itself is 01111111.
Invert and add 1
Here is the two's complement of 127 at 8 bits, step by step (invert the bits of 127 and add 1):
- Write 127 in 8-bit binary:
01111111. - Invert every bit (the one's complement):
10000000. - Add 1:
10000001.
127 at 4, 8, and 16 bits
| Width | 127 as a signed number | Two's complement of 127 |
|---|---|---|
| 4-bit | — | — |
| 8-bit | 01111111 | 10000001 |
| 16-bit | 0000000001111111 | 1111111110000001 |
A dash means 127 (or its negation) is outside that width's signed range: 4-bit two's complement holds -8 to 7, 8-bit holds -128 to 127, and 16-bit holds -32768 to 32767.
Convert any number
Two's complement is how computers store signed integers, so one adder can both add and subtract. Read the full two's complement lesson, or convert any value at 8, 16, or 32 bits with the two's complement calculator.
Want to see two's complement do real work? Open the lab and wire a subtractor from an adder and inverters, or follow the free course from a transistor up to an 8-bit CPU.
Open the two's complement calculator →Frequently asked
What is the two's complement of 127?
The 8-bit two's complement of 127 is 10000001, the bit pattern for -127. You get it by writing 127 in binary (01111111), inverting every bit (10000000), then adding 1.
How do you write 127 in two's complement?
127 in 8-bit two's complement is 01111111. Positive numbers are identical to plain binary, so no inverting is needed. At 16 bits it is 0000000001111111.
What is 127 in 16-bit two's complement?
127 in 16-bit two's complement is 0000000001111111. Two's complement sign-extends a shorter value by copying the sign bit to the left, so the value is unchanged from its 8-bit form.