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Digital Storage Units Explained: Bytes, KB, MB, GB, and TB

A drive box says 1TB, but your computer shows less. It's not a scam β€” it's two different ways of counting the same units.

A bit is the smallest unit; 8 bits make a byte

A bit is a single binary 0 or 1, the most basic unit a computer works with. Group 8 bits together and you get a byte, roughly enough to represent one character of text β€” the unit almost everything else is built from.

KB, MB, GB, and TB each jump by about a thousand

Kilobyte, megabyte, gigabyte, and terabyte form a ladder where each step is roughly a thousand times the one before it: about 1,000 bytes in a kilobyte, 1,000 kilobytes in a megabyte, and so on up through a terabyte.

Storage makers and operating systems count differently

Drive manufacturers use the decimal definition (1 GB = 1,000,000,000 bytes), while most operating systems calculate free space using the binary definition (1 GiB = 1,073,741,824 bytes) but often still label it "GB" on screen. That mismatch is the entire reason a "1TB" drive shows up as roughly 931GB in your file explorer β€” no space actually went missing.

Internet speeds are measured in bits, not bytes

An advertised "100 Mbps" connection means 100 megabits per second, not megabytes. Since a byte is 8 bits, that connection tops out around 12.5 megabytes per second in practice, which is why dividing an advertised speed by 8 gives a rough real-world download estimate.

What common files actually weigh

A short text email is a few kilobytes, a typical smartphone photo runs a few megabytes, a compressed song is roughly 3-5 megabytes, and an hour of HD video commonly lands in the low single-digit gigabytes β€” useful reference points for estimating how much storage or data a task will use.

Why your drive never shows the full number

The gap between an advertised "1TB" and the roughly 931GB your computer reports is not lost storage β€” it comes from manufacturers using clean decimal math (multiples of 1,000) while operating systems calculate free space in binary (multiples of 1,024), then label the binary result with the same "GB" or "TB" unit name. The bytes are all still there; only the counting convention differs.

Bigger than a terabyte: petabytes and beyond

As storage needs keep growing, the same thousand-times pattern continues past terabyte into petabyte, exabyte, and beyond, though those units rarely show up outside data centers and large-scale cloud storage. For nearly all personal and everyday computing, gigabytes and terabytes cover the practical range.

Frequently Asked Questions

Is 1 gigabyte equal to 1,000 or 1,024 megabytes?

Technically, 1,000 megabytes make a decimal gigabyte (GB), while 1,024 mebibytes (MiB) make a binary gibibyte (GiB) β€” but in everyday use, "gigabyte" is often used loosely to mean either, which is the root of most storage-size confusion.

Why does my new phone or laptop show less storage than advertised?

Part of it is the decimal-versus-binary counting difference described above, and part of it is that some space is used by the operating system, pre-installed apps, and system files before you ever store anything yourself.