You’ve probably wondered why are the computer drives smaller than advertised. If you’ve ever gone to buy a hard drive or SSD and you went to plug it in, you may have noticed that something doesn’t add up. If it’s a 1 TB drive, it’ll only show as 931GB. If it’s a 2 TB drive, it’ll only show as 1.81 TB, and so on.
So what gives? Surely this is false advertising by the manufacturers, but actually, it’s not.
They are telling the truth. The discrepancy comes from the units being used. There are some other possible reasons you will find out soon.
Reasons Computer Drives Smaller Than Advertised
So first let’s discuss why this discrepancy happens, and then we can get into the philosophical discussion about who’s right and who’s wrong. Below are the reasons why computer drives are smaller than advertised:
The Different Units
So let’s take a 1 TB drive. For example, One Terabyte (1 TB) is equal to a Thousand Gigabytes (1000 GB) now stop before some of you rush to the comments to say “it’s not a thousand” I’m going to address it. Now everyone has heard of Kilobyte, Megabyte, Gigabyte, and Terabyte with the abbreviations of KB, MB, GB, and TB.
But have you ever heard of Kibibyte, Mebibyte, Gibibyte, and Tebibyte? Yes. They’re actually a thing and they use the abbreviation KiB, MiB, GiB, and TiB.
The difference between them in terms of the number of bytes is that Megabytes and the others are powers of ten, whereas Mebibytes and the others are powers of two.
So there are 1024 Kibibytes in a Mebibytes, 1024, Mebibytes in a Gibibytes, and so on. And while they’re pretty close in actual numbers of bytes, the higher you go, the more they diverge.
The reason, for example, that a 1 TB drive shows up as 931GB in Windows is that behind-the-scenes windows measure the number of Gigabytes or whatever in terms of Gibibytes, but it incorrectly displays the labels as Gigabytes, and the same goes for Terabytes. It’s measuring and displays the number of Tebibytes but the units show Terabytes.
And since a Gibibyte is larger than a Gigabyte 1.074 times actually. If you divide one thousand GB by 1.074, you get the number 931. That’s where that comes from.
So if you buy a 1 TB drive, you are indeed getting 1 trillion bytes of storage. Now, side note many people would say that Windows isn’t actually rolling and displaying these units.
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Why Does Not Windows Use TiB and GiB?
Now you might be thinking, Wait, why doesn’t? Windows use the right units. And why haven’t I even heard of these Gibibytes and everything else before? Well, since the early days of computers, because computers use binary, it’s easier to actually deal with numbers in powers of two.
And you probably recognize these numbers they come a lot when you deal with computers and when they got to 1024 bytes, long story short, people decided, that’s close enough to 1000. We’ll just call it a kilobyte. And since every ten powers of two is close to its corresponding decimal number anyway, the other prefixes could just be used too.
This predictably became confusing for people using the terms megabytes and gigabytes and everything else for both the binary meaning and the decimal meaning. Binary with the powers of two meaning and Decimal as the power of ten meaning, but still calling them the same thing gigabytes and megabytes and whatever.
So the IEC, a standards organization, came up with those new prefixes to be used for the binary base units instead.
So you could discriminate between them and they came up with the names by just taking the “Bi” part of binary and sticking that on and using that. The problem is those units never really caught on in the mainstream. They are actually officially recognized, though. For example, the National Institute for Standards and Technology requires binary prefixes to be used if you’re referring to such units. But as the difference between the binary and decimal units became large. Many companies and people just started using the decimal meaning only, which is way more way intuitive. And that way they can just keep using the same unit labels.
For example, in 2009, starting with Mac OS 10.6, Macs used decimal units with their proper prefix. And since at least 2010 the Linux distribution Ubuntu has also had the policy to use the official units. So if you’re using a Mac or most distributions of Linux, then you’ll probably see the same number that shows on the box. I believe hard drive manufacturers have always used bed decimal meaning. And also if you’re talking about network speed like one gigabit per second, that has always referred to the decimal meaning. Also. So a big reason why you rarely see these units and prefixes is that most people aren’t using them anyway, they’re just using the decimal meaning of gigabytes.
Holdouts
There are some holdouts, though, who are using the binary units but displaying the decimal label, namely Microsoft Windows and Ram manufacturers as big ones. At least in Windows if you do go to the properties window of a directory or file, it will show you the exact number of bytes.
But for most people, I think that is just going to add to the confusion. So why does Windows do this? Well, if you go back to 2009, the reasoning was that nobody else was. So okay, fair enough. At the time, you could make the consistency argument. That blog post was from before Mac OS had even switched over later that year. But why Windows? Still, does this really confuses me?
And I’m not even saying that I expect them to start using the binary labels that would just confuse virtually everyone. Rather behind the scenes, they could start just showing and measuring in decimal units and keep the same label. And honestly, no one would even notice or care. There’s not anyone out there who would say, Wait a minute. This Microsoft Word document was 128 megabytes yesterday, and now it’s 1.34. What gives? Surely a lot of people would notice that their hard drive capacity has changed, but it would look like their hard drive got bigger.
So if Microsoft is maybe worried that a change after this long would be confusing to people. Well, I would argue there’s nothing confusing about it. The same number that’s listed on the box that you’re expecting. I mean, I remember even ages ago buying a 64-megabyte memory card for the Xbox 360 and being pissed when I plugged it in and saw there were only 61, seemingly because back then every megabyte mattered.
And even if there is some compatibility issue behind the scenes with how settings or Windows operates. What you could do is just change how it’s displayed in Windows Explorer only, which is what would matter to 99% of people. And then just keep using the binary units for any calculations behind the scenes and you could even switch those over to use the binary label.
Now I mentioned Ram manufacturers before and they also use capacities in powers of Two and display the decimal unit labels. Apparently, they do have a legitimate reason for using the binary units, at least because of the way logical and physical addressing works in memory. But I still think they should use the right labels and call them the right thing.
Other Possible Causes
Finally, in the beginning, I did mention that there are some other possible causes for why a drive might show a lower storage capacity. One of them is a hidden partition. A lot of prebuilt computers will come with a recovery partition that’s hidden and that will make the main partition show smaller. But that’s because it’s actually being used for something else.
I’ve seen some people mention that the operating system will take up space, but that wouldn’t actually reduce the capacity of the drive. That’ll just show as space taken up. Others have pointed out that the file system itself, like NTFS makes, takes up space on the drive. And while technically true, that would be relatively negligible, especially the difference compared to the units that are showing differently.
And also I’m not even sure if that would reduce the. Total capacity shown or if that would also just show as space taken up. In any case, hopefully, this cleared something up. And if you’re mad about drives not being as big as they should be, well, rest assured you are getting what you pay for at least most of the time.