From https://en.wikipedia.org/wiki/Kilobyte,
---------------------------------------------------------
Decimal || Binary
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Value | Metric || Value | IEC | JEDEC
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1000 | kB kilobyte || 1024 | KiB kibibyte | KB kilobyte
Also,"In the International System of Units (SI) the prefix kilo means 1000; therefore, one kilobyte is 1000 bytes. The unit symbol is kB."
"The binary meaning of the kilobyte for 1024 bytes typically uses the symbol KB, with an uppercase letter K."
"In December 1998, the IEC addressed such multiple usages and definitions by creating prefixes such as kibi, mebi, gibi, etc., to unambiguously denote powers of 1024. Thus the kibibyte, symbol KiB, represents 210 bytes = 1024 bytes."
On macOS Catalina 10.15.7:
$ head -c 92160 /dev/urandom > foo
$ ls -l foo
-rw-r--r-- 1 susam staff 92160 Dec 29 15:04 foo
$ ls -lh foo
-rw-r--r-- 1 susam staff 90K Dec 29 15:04 foo
On Debian GNU/Linux 10.6 (buster): $ head -c 92160 /dev/urandom > foo
$ ls -l foo
-rw-r--r-- 1 susam susam 92160 Dec 29 09:35 foo
$ ls -lh foo
-rw-r--r-- 1 susam susam 90K Dec 29 09:35 foo
$ ls -lh --si foo
-rw-r--r-- 1 susam susam 93k Dec 29 09:35 foo
$ sudo cp foo /var/www/html/foo
$ wget http://127.0.0.1/foo -O /dev/null
--2020-12-29 09:41:05-- http://127.0.0.1/foo
Connecting to 127.0.0.1:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 92160 (90K) [application/octet-stream]
Saving to: '/dev/null'
/dev/null 100%[===================>] 90.00K --.-KB/s in 0s
2020-12-29 09:41:05 (845 MB/s) - '/dev/null' saved [92160/92160]
This 90 kB (92 KiB) is also hosted temporarily at http://172.105.48.21/foo . When Firefox downloads it shows 90 KB in the Developer Tools > Network tab as well as in the download box [1]. However, after the file is downloaded, macOS Finder shows the file to be of 92 KB [2].Note that on OpenBSD "df" shows space in "blocks" by default, which pretty much nobody wants.
Hard drives are sold in real units for decades.
And floppies of "1.44MB" were always 1000 times 1024 times 1.44 bytes. Madness, eh?
So make it 10000 bytes, then. That way it's easier to calculate how long it takes to transmit on the wire, since network speeds have always been 1000-based.
Edit: yes, I'm probably getting the pre-decimalization math wrong above, since I'm likely confusing pre-decimalization pence with post.
In 1971, a cheap paperback book was sold for two shillings and sixpence, which was said as 'two-and-six'. Decimalisation [0] was my first experience of price gouging, when the same paperbacks were suddenly repriced at 15p (~three shillings) instead of the 12.5p which was the decimal equivalent of their old price.