Why a kilobyte is 1000 and not 1024 bytes

A lot of people are replying as if OP asked a question. It's a link to a blog post explaining why a kilobyte is 1000 and not 1024 bytes (exactly as the title says!). OP knows the answer, in fact they know it so well they wrote an extensive post about it.

Thank you for the write up! You should re-check the spelling and grammar as some sections had some troubles. I have a sentence I need to go to the post to get, so let me edit this later!

Edit: the second half of this sentence is a mess: "The factors don’t solely consist of twos, but ten are certainly lot of them." Otherwise nothing jumped out at me but I would reread it just in case!

Well it’s because computer science has been around for 60+ years and computers are binary machines. It was natural for everything to be base 2. The most infuriating part is why drive manufacturers arbitrarily started calling 1000 bytes a kilobyte, 1000 kilobytes a megabyte, and 1000 megabytes a gigabyte, and a 1000 gigabytes a terabyte when until then a 1 TB was 1099511627776 bytes. They did this simply because it made their drives appear 10% bigger. So good ol’ shrinkflation. You could make drives 10% smaller and sell them for the same price.

I genuinely don't understand your disdain for using base 2 on something that calculates in base 2. Do you know how counting works in binary? Every byte is made up of 8 bits, and goes from 0000 0000 to 1111 1111, or 0-15. When converted to larger scales, 1024 bytes is a clean mathematical derivation in base 2, 1000 is a fractional number. Your pedantry seems to hinge on the use of the prefix right? I think 1024 is a better representation of kilo- in base 2, because a kilo- can be directly translated up to exabytes and down to nybbles while "1000" in base 2 is extremely difficult. The point of metric is specifically to facilitate easy measuring, right? So measuring in the units that the computer uses makes perfect sense. It's like me saying that a kilogram should be measured in base 60, because that was the original number system.

I was confused when I just read the headline. Should be "Why I (that would be you not me) think a kilobyte should be 1000 instead of 1024". Unpopular opinion would be a better sub for it.

Here’s my favorite part.

“In addition, the conversions were sometimes not even self-consistent and applied completely arbitrary. The 3½-inch floppy disk for example, which was marketed as “1.44 MB”, was actually not 1.44 MB and also not 1.44 MiB. The size of the double-sided, high-density 3½-inch floppy was 512 bytes per sector, 18 sectors per track, 160 tracks, that’s 512×18×16 = 1’474’560 bytes. To get to “1.44” you must first divide 1’474’560 by 1024 (“bEcAuSE BiNaRY obviously”) to get 1440 and then divide by 1000 for perfect inconsistency, because dividing by 1024 again would get you an ugly number and we definitely don’t want that. We finally end up with “1.44”. Now let’s add “MB” because why the heck not. We already abused those units so much it’s not like they still mean anything and it’s “close enough” anyways. By the way, that “close enough” excuse never “worked when I was in school but what would I know compared to the computer “scientists” back then.

When things get that messy, numbers don’t even mean anything any more. Might as well just label the products using entirely qualitative terms like “big” or “bigger”.

Thanks for this article. Unfortunately, you used the word “prefix” when you really meant “unit symbol”. So, “kilo” and “mega” are prefixes, kB and MB are unit symbols. You repeatedly called the latter “prefixes”.

Stop blaming drive manufacturers

The most scientific shill I've seen in a while

CC BY-NC-SA 4.0

I know it's already been explained but here is a visualization of why.

0 2 4 8 16 32 64 128 256 512 1024

You asked for feedback, so here is my feedback:

The article is okay. I read most of it, but not all of it, because it seemed overly worded for the sentiment. It could have been condensed quite a bit. I would argue the focus should be more on the fact that there should be a standard in technical documentation, OS's, specification sheets, etc. That's the part that impacts most people, and the reason they should care. But that kind of gets lost in all the text.

Your replies here come off as pretty condescending. You should anticipate most people not reading the article before commenting. Just pay them no attention, or reiterate what you already stated in the article. You shouldn't just say "did you read the article" and then "it's in this section of the article". Just like how people comment on youtube before watching the video, people will comment on the topic without reading the article.

Maybe they didn't realize it was an article, maybe they knew it was an article and chose not to read it, or maybe they read it and disagree with some of the things you said. It's okay for people to disagree with something you said, even if you sincerely believe something you said isn't a matter of opinion (even though it probably is). You can agree to disagree and move on with your life.

you can't ask for feedback, then attack everyone who doesn't share your opinion with "did you read it?", that's not cool...

A kilobyte (kB) is 1000 bytes, that's what the prefix kilo means. A kibibyte (KiB) is 1024 bytes (the "bi" in the prefix means base 2 or binary). People often confuse them, but they're similar enough for smaller units, 10^3 ~ 2^10.

Oh and at first, kilobyte was used for both amounts, which is why kibibytes were introduced to fix the confusion, which perhaps was a bit late anyway.

The mistake is thinking that a 1000 byte file takes up a 1000 bytes on any storage medium. The mistake is thinking that it even matters if a kB means 1000 or 1024 bytes. It only matters for some programmers, and to those 1024 is the number that matters.

Disregarding reality in favor of pedantics is the real mistake.

I suggest considering this from a linguistic perspective rather than a technical perspective.

For years (decades, even), KB, MB, GB, etc. were broadly used to mean 2^10, 2^20, 2^30, etc. Throughout the 80s and 90s, the only place you would likely see base-10 units was in marketing materials, such as those for storage media and modems. Mac OS exclusively used base-2 definitions well into the 21st century. Windows, as noted in the article, still does. Many Unix/POSIX tools do, as well, and this is unlikely to change.

I will spare you my full rant on the evils of linguistic prescriptivism. Suffice it to say that I am a born-again descriptivist, fully recovered from my past affliction.

From a descriptivist perspective, the only accurate way to define kilobyte, megabyte, etc. is to say that there are two common usages. This is what you will see if you look up the words in any decent dictionary. e.g.:

I don't recall ever seeing KiB/MiB/etc. in the 90s, although Wikipedia tells me they "were defined in 1999 by the International Electrotechnical Commission (IEC), in the IEC 60027-2 standard".

While I wholeheartedly agree with the goal of eliminating ambiguity, I am frustrated with the half-measure of introducing unambiguous terms on one side (KiB, MiB, etc.) while failing to do the same on the other. The introduction of new terms has no bearing on the common usage of old terms. The correct thing to have done would have been to introduce two new unambiguous terms, with the goal of retiring KB/MB/etc. from common usage entirely. If we had KiB and KeB, there'd be no ambiguity. KB will always have ambiguity because that's language, baby! regardless of any prescriptivist's opinion on the matter.

Sadly, even that would do nothing to solve the use of common single-letter abbreviations. For example, Linux's ls -l -h command will return sizes like 1K, 1M, 1G, referring to the base-2 definitions. Only if you specify the non-default --si flag will you receive base-10 values (again with just the first letter!). Many other standard tools have no such options and will exclusively use base-2 numbers.

Because SI prefixes are always powers of the base. Base 10 is the most common, but that's more human psychology that math.

Because a kilo is 1000. That's why you have kibi, mebi, gibi binary prefixes for those times where 1024 (power of 2's) matter.

This is the stupid af.

It's a scam by HDD makers to sell less storage for more money.

This has been my pet rant for a long time, but I usually explain it .. almost exactly the other way around to you.

You can essentially start off with nothing using binary prefixes. IBM's first magnetic harddrive (the IBM 350 - you've probably seen it in the famous "forklifting it into a plane" photo) stored 5 million characters. Not 5*1024*1024 characters, 5,000,000 characters. This isn't some consumer-era marketing trick - this is 1956, when companies were paying half a million dollars a year (2023-inflated-adjusted) to lease a computer. I keep getting told this is some modern trick - doesn't it blow your mind to realise hdd manufacturers have been using base10 for nearly 70 years? Line-speed was always ~~a lie~~ base 10, where 1200 baud laughs at your 2^n fetish (and for that matter, baud comes from telegraphs, and was defined before computers existed), 100Mbit ethernet runs on a 25MHz clock, and speaking of clocks - kHz, MHz, MT/s, GT/s etc are always specified in base 10. For some reason no-one asks how we got 3GHz in between 2 & 4GHz CPUs.

As you say, memory is the trouble-maker. RAM has two interesting properties for this discussion. One is that it heavily favours binary-prefixed "round numbers", traditionally because no-one wanted RAM with un-used addresses because it made address decoding nightmarish (tl;dr; when 8k of RAM was usually 8x1k chips, you'd use the first 3 bits of the address to select the chip, and the other 10 bits as the address on the chip - if chips didn't use their entire address space you'd need to actually calculate the address map, and this calculation would have to run multiples of times faster than the cpu itself) . The second, is that RAM was the first place non-CSy types saw numbers big enough for k to start becoming useful. So for the entire generation that started on microcomputers rather than big iron, memory-flavoured-k were the first k they ever tasted.

I mean, hands up who had a computer with 8-64k of RAM and a cassette deck. You didn't measure the size of your stored program in kB, but in seconds of tape.

This shortcut than leaked into filesystems purely as an implementation detail - reading disk blocks into memory is much easier if you're putting square pegs into square holes. So disk sectors are specified in binary sizes to enable them to fit efficiently into memory regions/pages. For example, CP/M has a 128-byte disk buffer between 0x080 and 0x100 - and its filesystem uses 128-byte sectors. Not a coincidence.

This is where we start getting into stuff like floppy disk sizes being utter madness. 360k & 720k were 720 and 1440 512-byte sectors. When they doubled up again, we doubled 2800 512-byte sectors gave us 1440k - and because nothing is ever allowed to make sense (or because 1.40625M looks stupid), we used base10 to call this 1.44M.

So it's never been that computers used 1024-shaped-k's. It should be a simple story of "everything uses 1,000s, except memory because reasons". But once we started dividing base10-flavoured storage devices into base2-flavoured sectors, we lost any hope of this ever looking logical.

This whole mess regularly frustrates me... why the units can't be used consistently?!

The other peeve of mine with this debacle is that drive capacities using SI units do not use the full available address space (since it's binary). Is the difference between 250GB and 256GiB really used effectively for wear-levelling (which only applies to SSDs) or spare sectors?

Nice to learn about the SI standard notation KiB, MiB, etc. I had no idea.

I was taught 1024 in my tech school. So I won’t ever refer to it as 1000 instead 1024. Not that it seems even remotely relevant though.

WD needed to sell a drive with more advertised space than real space.

It is only a mistake from a Human PoV. It is more efficient for the chip since 1000 bytes and 1024 bytes take up the same space. But Humans find anything not base 10 difficult.

Unlike many comments here, I enjoyed reading the article, especially the parts in the "I don’t want to use gibibyte!" chapter, where you explain that this (the pedantry) is important in technical and formal situations (such as documentation). Seeing some of the comments here, I think it would have helped to focus on this aspect a bit more.

I also liked the extra part explaining the reasoning for using the Nokia E60.

I don't quite agree with the recommendation to use base 10 SI units where neither KiB or kB would result in nice numbers. I don't see why base 10 should have an influence on computers, and I think it makes more sense to stick to a single unit, such as KiB.

The reasons I have this opinion are probably to do with:

My computer has shown me values using KiB, Gib, etc for years - I think it's a KDE default - so I'm already used to the concept of KiB being different from kB.
I dislike the concept of base 10 in general. I like the idea of using base 16 universally (because computers. Base 12 is also valid in a less computer-dominant society). I therefore also think 1024 is a silly number to use, and we should measure memory in multiples of 2^8 or 2^16...

p.s, I agree with other commenters that your comments starting with "Pretty obvious that you didn’t read the article." or similar are probably not helping your case... I understand that some comments here have been quite frustrating though.

Permanently Deleted

Kilobyte is 2^10 bytes or about a thousand bytes within a few reasonably significant digits.
Megabyte is 2^20 bytes or about a thousand megabytes within a few reasonably significant digits.
Terabyte is 2^30 bytes or about a a thousand megabytes within a few reasonably significant digits.

The binary storage is always going to be a translation from a binary base to a decimal equivalent. So the shorthand terms used to refer to a specific and long integer number should comes as absolutely no surprise. And that's just it; they're just a shorthand, slang jargon that caught on because it made sense to anyone that was using it.

Your whole article just makes it sound like you don't actually understand the math, the way computers actually work, linguistics, or etymology very well. But you're not really here for feedback are you. The whole rant sounds like a reaction to a bad grade in a computer science 101 course.

i mean, you can't get to 1000 by doubling twos, so, no?

Reality doesn't care what you prefer my dude

The only place where kilobyte is 1000 bytes has been Google and everywhere else it's 1024 so even if it's precise I don't see the advantage of changing usage. It would just cause more confusion at my work than make anything clearer.

Based on your other replies, no, I absolutely will not waste my time reading your opinion piece.

And, a blog post is just another way of saying this is your opinion. That's all it is.

Because Kilo means 1000

....wait why is it not 1000 in the first place? Is this some kind of rounding thing?????

It is really not that difficult. Kilo is always thousand.

1.000 grams = 1 kilogram

1.000 meters = 1 kilometer

Maybe it’s harder for Americans with their fantasy units.