How this works

File sizes can be counted two different ways: decimal (1,000 bytes per KB), which is what drive manufacturers and most marketing materials use, or binary (1,024 bytes per KB), which is what your operating system typically displays. This mismatch is exactly why a "1TB" hard drive shows up as roughly 931GB in your file explorer — both numbers are correct, they're just counting differently.

Frequently asked

Why does my new drive show less space than advertised?

Drive manufacturers advertise capacity using decimal (1000-based) units, while your operating system displays it using binary (1024-based) units — the drive isn't missing space, it's just two different counting conventions for the same physical storage.

Which should I use for file uploads or email attachments?

Most upload limits and attachment size caps are stated in decimal megabytes, though it's worth checking the specific service — when in doubt, decimal is the more common convention online.