Why a 500 GB drive shows 465 GB

Nothing is missing, and nobody cheated you. The drive manufacturer and your operating system are counting in different units, and both are technically right.

Two kinds of "kilo"

• Decimal (SI): 1 KB = 1000 bytes, 1 MB = 1000 KB, 1 GB = 1000 MB. This is what storage is sold in, what network speeds use, and what the word "kilo" means everywhere else in life.
• Binary (IEC): 1 KiB = 1024 bytes, 1 MiB = 1024 KiB, 1 GiB = 1024 MiB. Computers address memory in powers of two, so this is what Windows and many programs actually display — usually while writing it as "GB".

Run the numbers: 500,000,000,000 bytes ÷ 1024³ = 465.7 GiB. The gap grows with size: about 2.4% at kilobytes, 7.4% at gigabytes, 10% at terabytes.

Where this bites in practice

• Upload limits. "Max 25 MB" almost always means 25 decimal megabytes. A file your computer shows as 24 MiB is 25.2 MB and gets rejected — which is exactly the moment people conclude the site is broken.
• Video. A "100 MB" limit on a messenger is decimal. Compress to about 95 MB as your computer counts it and you will be comfortably inside.
• Email attachments. A 25 MB limit applies after base64 encoding, which inflates a file by roughly 33%. Your practical ceiling is closer to 18 MB.

The honest summary

macOS switched to decimal years ago, which is why the same file looks larger on a Mac than on a Windows machine. Linux tools vary by tool. Nobody is going to fix this, so the useful habit is to look at the actual byte count when a limit is close, and to leave 10% of headroom whenever a service quotes a maximum.