Hard drive manufacturers have been doing this for decades. This is why the “80GB” drives were 74.5GB in Windows.

It’s more complicated with SSDs: https://www.anandtech.com/show/2829/7

EDIT: the official “kibibyte” was standardized in 1998: https://physics.nist.gov/cuu/Units/binary.html so almost 20 years ago. Blame Windows and HDD mfgs for sticking with the SI definitions.

Yea, bad bad windows for following standards.

The SI prefixes are well established before 1998 and the cause for this brainmelt.

https://en.wikipedia.org/wiki/Metric_prefix

Windows (at least up to 8) does not follow the SI standard. It uses KB, MB, GB but converts using 1024. Which has funny consequences, like 999MB being smaller 0.94GB.

Well to be fair “GB” could refer to either prefix.