# What’s the real capacity?

2TB is an accurate description, assuming 1TB = 1,000,000,000,000 bytes

Beyond that, there are some complexities to how hard drive capacities are stated, so read on if that interests you…
There is no confusion over bits and bytes – a bit is a single binary value of ‘1’ or ‘0’, and a byte is eight of those.

In SI units and speaking in base 10 the following is true:

• KB, Kilobyte = 1,000 bytes   (10^3)
• MB, Megabyte = 1,000,000 bytes  (10^6)
• GB, Gigabyte = 1,000,000,000 bytes  (10^9)
• TB, Terabyte = 1,000,000,000,000 bytes  (10^12)

In common computing usage, base 2 is more practical than base 10.  As a result, 1024 replaces 1000 as a Kilobyte without much significant effect. However, scaling this to Terabytes results in a substantial discrepancy.  This has largely been addressed across operating systems, but users are often unfamiliar with the binary unit names since the decimal units are so ubiquitous and so often abbreviated.

Properly named the units in base 2 are as follows:

• KiB, Kibibyte = 1,024 bytes  (2^10)
• MiB, Mebibyte = 1,048,576 bytes  (2^20)
• GiB, Gibibyte = 1,073,741,824 bytes  (2^30)
• TiB, Tebibyte = 1,099,511,627,776 bytes  (2^40)

So, for example, the Longtake mag in a MacOS system will read as 2TB, while in the RED camera interface, it will be displayed as 1.8TiB.  Both of these values are 2,000,000,000,000 bytes.