Why is the hard drive capacity always lower than the manufacturer says?

It is fairly certain that most of us have realized that the actual capacity of the hard drive in our computer is not the same as the number listed on the box: 1TB HDD but the actual capacity is only 931GB, or SDD 250GB but in OS install drive only has 232GB. Even with mobile devices like iPhone 64GB, the memory you can use is only about 56GB only.

There are several reasons - of course good - to explain this. Let's see why the actual capacity is often not the same as what is advertised.

Pre-installed operating system and application

One of the most common reasons is that there is already a fair amount of data available when you buy a new device . Of course it does not apply to Flash or SD drives, but phones and PCs, laptops with pre-installed operating systems or software.

When we buy a computer, the operating system (Windows or MacOS) takes up a large amount of hard drive space. Files and directories belonging to the operating system are necessary for the computer system to function properly. Therefore, we do not need to be too upset with this problem.

The following example shows us that C: / Windows operating system data alone takes up 25GB, nearly 1/10 of the space of a 256GB SSD.

However, in some cases, the space utilization comes not just from OS files. Most operating systems also include a number of built-in apps that you can use if you like, including bloatware - trial applications - from Windows or some useful software pre-installed on macOS. like GarageBand. These software are not actually part of the operating system, so you can optionally remove to free up memory space for your device.

Computers measure memory space differently than us

While pre-installed apps are one of the main factors, the biggest reason users don't get all the storage they have is because computers have a completely different way of measuring metrics. people.

Interpret the binary numbers

The calculator uses standard value prefixes, including "kilo" instead of thousand, "mega" instead of million, "giga" - billion and "tera" - trillion . First, we will clarify how much gigabytes will become 1 terabyte.

For human beings, including hardware manufacturers, all use the decimal system, measured with a base multiple of 10. Therefore, when we say "500 gigabytes", that means 500 trillion bytes.

However, unlike us, computers use a 2-character binary system, representing all numbers with only 1 and 0.

From 1 to 10 in binary form is expressed as follows:

1: 20 = 1

10: 20 + 21 = 2

11: 20 +21 = 3

100: 20 + 21 +22 = 4

101: 20 +21 +22 = 5

110: 20 + 21 +22 = 6

111: 20 +21 +22 = 7

1000: 20 + 21 +22 +23 = 8

1001: 20 +21 +22 +23 = 9

1010: 20 + 21 +22 +23 = 10

As you can see, in binary, 21 represents a decimal value of 1, 22 has a value of 4, 23 has a value of 8, 24 is equivalent to 16, and so on. Each new digit position in binary increases the value of the decimal by 2x. And finally, 210 equals 1024.

Compute binary and decimal

We now know why computers use 1024 instead of 1000 to determine the measurement prefixes above. 1024 bytes is equivalent to 1 Kilobyte (KB) rather than 1000 as a decimal. Similarly, 1 Megabyte (MB) would be equal to 1024 KB, and 1 Gigabyte (GB) would be equal to 1024 MB .

Let's get back to the problem, assuming we have a removable SSD drive with the capacity written on the box 250GB. That drive will hold a total of 250,000,000,000 bytes, but when inserted into a computer, they won't display that way.

To do the conversion, we divide the number by 1,024 three times: divide one time to convert from GB to MB, divide 2 times to convert from MB to KB, and divide the last time to convert from KB to B.

250,000,000,000/ (1,024 * 1,024 * 1,024) = 232,830,643,653 bytes, or 232.83 GB

A 250GB disk test in Windows showed that its maximum capacity was 232 GB, the result was exactly what we calculated, with a difference of about 18GB. The larger the drive capacity, the greater the difference between the nominal memory space and the actual memory space. For example, with a 1TB (1000GB) drive, only about 931GB is shown on the computer.

Gigabyte and Gibibyte

At this point, many people will wonder: so why does this difference exist? Why are hard drive manufacturers not disclosing their actual capacity levels, is there anything difficult that makes them do so?

No, of course, they can absolutely announce the actual capacity of the drive.

The best definition of the concept of "giga" is a multiple of 1000. As for 1024 we have another name: "Gibi". The International Electrotechnical Commission (IFC) has set a common standard for calculating binary data to address these backlog problems.

Accordingly, 1 Kilobyte (KB) will be equal to 1000 bytes, while 1 Kibibyte (KiB) will be equal to 1024 bytes. Similar to the prefixes expressing higher capacity, such as Mebibyte (MiB), Gibibyte (GiB), Tebibyte (TiB) .

For some reason, Windows was incorrect to use "GB" to show the true value of gibibytes. Other operating systems, such as macOS, already exhibit quite a 1GB standard, which is equivalent to one billion bytes. So, the same 250GB drive, while Windows gives 232GB, the Mac will show the correct capacity of 250GB in the machine.

Additional hard drive partition

In addition to the main reasons outlined above, there is another secondary cause - though not common - that can also cause a reduction in disk space: additional partitions.

In case you still do not know, we can completely divide the hard drive into many different logical areas, also known as hard drive partitions. Dividing the hard drive into multiple zones allows us to install two different operating systems on the same drive, for specific use purposes.

When a user buys a laptop or a computer already installed, the manufacturer will usually create a recovery partition on the drive. This area will contain data that allows users to reset the operating system in cases of force majeure. Similar to other files, they will occupy part of the hard drive memory space. However, because the recovery partition is often hidden on Windows, you probably won't realize this area exists.

To find out where your drives are on Windows, type disk management in the search bar and select Create and format hard disk partitions . Here you can see all the drives on the system like HDD, SSD and even partitions created. If any partition has Restore, Recovery properties, then that is the area containing the recovery data for your device.

In most cases, we can delete these partitions and bring the drive back to the amount we want. However, it is best to leave it that way, as the recovery partition will make it easier for us to restore the operating system, and a small footprint is not worth the trouble when Perform a computer restore manually.

Hidden features can also take up space

Finally, most operating systems are equipped with specific features that can take up space but do not exist certain executable files. For example, Windows's Shadow Copy has been included in Previous Versions and System Restore features.

System Restore allows the operating system to revert to a previous point if they are not working well, while Previous Version stores individual file copies so that you can undo the changes. And, of course, both of these features require memory space.

To check and change the amount of memory space of the above features, press Win + Pause to open the Control Panel dialog box. From here, select System Protection on the left. In the window that appears, select your drive from the list and select Configure .

In the System Protection dialog box that allows users to completely disable the system protection function (recommended not to select this item), the lower section displays the current capacity and adjust the maximum amount of Windows available. usable for Shadow Copy. 10% is a fairly good occupancy rate that you can consider in this case.

Conclude

These are the most common reasons that can explain the difference between actual and hard drive capacity, although there are some other small factors - such as special blocks in an SSD. - still not mentioned. Hopefully this article can help you to make some reasonable choices for choosing a drive with a capacity suitable for the purpose and needs of use.