A kilobyte is a unit for measuring digital information, equal to about 1,000 bytes. Think of bytes as the basic building blocks of computer data: a single letter or number takes up about one byte of space. A kilobyte can hold roughly 1,000 letters, which is about half a page of text.

The prefix kilo means one thousand, just like a kilometer equals one thousand meters. Computer scientists use kilobytes to measure how much information something contains or how much space it takes up. A short email might be a few kilobytes. A simple drawing could be 50 kilobytes.

Today, kilobytes seem tiny because files have gotten so much bigger. A single photo from a smartphone might be several megabytes (millions of bytes), and a movie could be several gigabytes (billions of bytes). But in the early days of computers, a kilobyte was significant. The first computers had only a few kilobytes of memory total, yet people still managed to write programs, play simple games, and process important calculations.

You'll often see kilobytes abbreviated as KB, like when a file shows its size as “45 KB.” Understanding kilobytes helps you grasp how digital information gets measured and stored, from the smallest text file to the largest video game.