From bits to bytes
The smallest unit of data is the bit, a single 0 or 1. A single bit cannot hold much, so bits are grouped together. Eight bits make one byte. One byte is enough to store one character, such as the letter A or the digit 7. So when you type your name, each letter takes about one byte of storage.
Key idea
1 byte = 8 bits. 1 kilobyte (KB) = 1024 bytes. 1 megabyte (MB) = 1024 KB. Each bigger unit holds 1024 of the unit below it.
Bigger units
Bytes are small, so we use larger units for bigger files. A kilobyte (KB) is 1024 bytes — about a short paragraph of text. A megabyte (MB) is 1024 KB — about one photo or one minute of music. We use 1024 (not 1000) because computers count in binary, and 1024 is a power of two.
Why measure data?
Knowing the size of data helps you decide if a file will fit on a phone, load quickly over the internet, or send in a message. A plain text message is only a few bytes, a photo is a few MB, and a long video can be hundreds of MB. Smaller data uses less storage and travels faster.
Example
The word DATA has 4 characters, so it needs about 4 bytes = 32 bits. A 2 KB note is 2 × 1024 = 2048 bytes.