Mirrorbits measures file sizes in MiB/GiB, but says it's using MB/GB

[Pointedstick]

KDE has an instance of mirrorbits, and we've noticed a mismatch in the size display: the unit being used is incorrect.

For example, https://files.kde.org/kde-linux/kde-linux_202512081900.raw.mirrorlist says:

The file /kde-linux/kde-linux_202512081900.raw has a size of 5.8 GB (6277021696 bytes) and was last modified on Mon, 08 Dec 2025 19:22:15 UTC.

"GB" is a "Gigabyte", which is exactly 1 billion bytes — a decimal metric unit. 6277021696 bytes is approximately 6.27 Gigabytes (GB), not 5.8.

6277021696 bytes is 5.8 of something, though. That something is a Gibibyte, with the abbreviation GiB. This is a binary IEC unit.

My preference would be to continue using Gigabytes/GB (as this is by far the more common unit of measurement), and make the number accurate.

[elboulangero]

It seems that the code that computes human-readable sizes is here:

mirrorbits/utils/utils.go

Lines 105 to 118 in 4125599

	// ReadableSize returns a file size in a human readable form
	func ReadableSize(value int64) string {
	units := []string{"bytes", "KB", "MB", "GB", "TB"}
	v := float64(value)
	for _, u := range units {
	if v < 1024 || u == "TB" {
	return fmt.Sprintf("%3.1f %s", v, u)
	}
	v /= 1024
	}
	return ""
	}

It's / 1024 so it's IEC units indeed. We can probably updates the units that are displayed on the web page, from "KB", "MB", "GB", "TB" to "KiB", "MiB", "GiB", "TiB".

My preference would be to continue using Gigabytes/GB (as this is by far the more common unit of measurement), and make the number accurate.

How do you know that this is "by far the more common unit of measurement"?

Personally I check file sizes in the my terminal with ls -lh or du -sh, and both give me IEC units. I'm running Linux, GNOME terminal.

If I download a file with Chromium, it also shows me IEC units in the "Downloads" drop-down menu. Right now, I'm downloading https://files.kde.org/kde-linux/kde-linux_202508202317.raw.mirrorlist and it tells me it's 5.9 GB, and the file is in fact 5.9 GiB.

A quick Google search tells me that both Firefox and Chromium do the same: they measure file sizes in IEC, but display the SI suffix, so when they show 5.9 GB they mean 5.9 GiB.

However if I open the GNOME file manager, it shows me file sizes in SI, with SI suffix. According to a quick Google search, GNOME uses SI, while KDE uses IEC. No idea about Windows, Mac, Android and such...

So at this point, I'd be tempted to do... nothing. If the status quo in web browsers is to show IEC sizes with SI suffix, be it. It's Ok if the mirrorbits web page do the same. I'd be Ok to display IEC suffixes for the sake of clarity.

@Pointedstick For the sake of the discussion, feel free to share what's your OS, and how it shows file sizes, I'm curious :)

[jbkempf]

For me, the suffix are currently correct: everyone has used GB and TB forever, since the beginning of FS to mean what GiB/TiB mean now for files size, including all non-open-source OSes.

The fact that they changed that later to make it match SI is unfortunate (and pedantic). Even ls -h defaults to IEC.

So, if you want, create an option to show GiB and MiB, instead of GB and MB. But changing from /1024 to /1000 is incorrectly IMHO.

[Pointedstick]

We can probably updates the units that are displayed on the web page, from "KB", "MB", "GB", "TB" to "KiB", "MiB", "GiB", "TiB".

That would be great! Then at least the units would be accurate.

It's less great that both the SI and IEC standards exist, but if the correct prefixes are used, then at least we know which is being used.

But the problem with using SI prefixes for IEC units (i.e. JEDEC, which is currently being used here) is that you don't know what the actual size is!

To my knowledge, in the OS space, only MS Windows uses JEDEC. Pretty much everyone else uses either SI or IEC:

• All of Apple's OSs use SI
• Android uses SI
• Ubuntu with GNOME uses SI (and GNOME uses it on other OSs too)
• KDE Plasma uses IEC

This was my basis for describing SI as "by far the more common unit of measurement".

So my own DE, KDE Plasma, is kind of the odd one out here, and over time I'd like to change it to SI. But I'd be okay with IEC being used by Mirrorbits because at least then the prefix would matche the unit!