Bits, bytes & storage

Your phone reports: storage almost full. But what do those 128 GB even mean, and why does that one video no longer fit? If you can read data sizes, you instantly know whether 500 MB is a lot or a little. That is exactly the feel you will get here.

Bit and byte

The bit is the smallest unit of information there is: a single yes-or-no decision, a 0 or a 1. Because a single bit says very little, 8 bits are grouped into one byte. One byte can represent 256 different values, enough for one letter, for example. All larger units build on the byte.

KB, MB, GB, TB: times 1000 each

The big units follow a simple staircase, each step is a factor of 1000: 1000 bytes are 1 kilobyte (KB), 1000 KB are 1 megabyte (MB), 1000 MB are 1 gigabyte (GB), 1000 GB are 1 terabyte (TB). So to convert, you just shift the decimal point by three places: 2500 MB is 2.5 GB. We always use 1000 here. Some programs, however, count internally in steps of 1024, which is why your computer often shows only about 3.6 TB for a 4 TB hard drive.

Typical file sizes in everyday life

With a few anchor values you can estimate almost anything: a text message needs only a few hundred bytes. A phone photo is about 3 MB, a song around 5 MB. A film in good quality needs several GB. This also explains your data plan: with 5 GB per month you can send more than a thousand photos, but stream only one or two films in good quality.