128 in binary
The decimal number 128 written in binary is 10000000. In hexadecimal it is 80, and in octal 200.
| Base | Value |
|---|---|
| Decimal (base 10) | 128 |
| Binary (base 2) | 10000000 |
| Hexadecimal (base 16) | 80 |
| Octal (base 8) | 200 |
How 128 converts to binary
Binary is base 2, so each place is worth twice the one to its right: 1, 2, 4, 8, 16, and so on. Adding up the place values that have a 1 gives back the decimal number:
128 = 128
That is why 128 in decimal is 10000000 in binary: it is exactly the set of powers of two that add up to 128. To get the hexadecimal form, group the bits into fours from the right and write each group as one hex digit, which gives 80.
Convert any number
Type any value and watch all three bases update live in the binary converter, or read the theory behind it in the lessons on binary numbers and hexadecimal.
Want to build the circuit that does this? Open the lab and wire up an adder, or follow the free course from a single transistor up to an 8-bit CPU.
Open the binary converter →Frequently asked
What is 128 in binary?
128 in binary is 10000000. That is the sum of the powers of two 128, which add up to 128.
What is 128 in hexadecimal?
128 in hexadecimal is 80. You get it by grouping the binary digits 10000000 into fours from the right and writing each group as one hex digit.
How many bits is 128?
128 needs 8 bits in binary (10000000). It fits in a single 8-bit byte.