Why is 1 kb 1024 bytes?

Computer understands binary system. One kilobyte written in binary is 10000000000. Two to the 10 power is equal to 1024 and that is how 1024 bytes came about.

The magic number in binary code is 8! Everything is divisible by this number. A byte would look like this 10001100. Basically, since in computing when we increase in size or compacity we double it.
So: 8+8=16; then 16+16=32; etc. until you reach 1024! This is because in a base 10 number system, each position signifies a power of ten. But the binary system is a base 2 and is absolute, which means the lowest value in an 8-bit binary position would 1 (2 to the 0 power) and the highest value would be 2 to the power of 7 which equals 128. 128 multiplied by 8 (the magic number!) is 1024!

Short for megabytes

Why is 1 kb 1024 bytes?

Well it isn't actually!

Bytes are bigger than bits because there are 8 bits in a Byte. You use 1024 when you move between bits & kilobits, or Bytes & kiloBytes or even kilobits to Megabits.

Saying it another way, there are 1024 bits in a kilobit & 1024 Bytes in a kiloByte.

The reason the number 1024 is used, is because in binary (computers math language) which works on the the base 2 numbering system you can't get the decimal number 1000. You can only get the number 1024 which is 2 to power 10 ie. 2x2x2x2x2x2x2x2x2x2 = 1024