What is a File Size? (Explained)

What is a File Size?

A file size indicates the space taken up by the file on the storage medium such as the hard drive, USB flash drive or even cloud storage. The file size can be measured in different units such as:

  • Bytes, denoted as B
  • Kilobytes, denoted as KB
  • Megabytes, denoted as MB
  • Gigabytes, denoted as GB
  • Terabytes, denoted as TB and more.

These units actually represent how much data can actually be stored in a given file.


  • The file size indicates the total storage space consumed by a file which can be in a hard drive, flash drive or even in the cloud.
  • Depending on the size, from smaller to larger, the file size is denoted as bytes, kilobytes, megabytes, gigabytes, terabytes, and more.
  • The file size can be converted easily according to the byte order by taking 1024 as the constant value and dividing smaller units and multiplying larger units by it.

Understanding File Size in Computer

Understanding File Size in Computer

The computers of today can store a lot more data than the ones that were available twenty years ago.

However, every computer comes with a definite amount of storage which may turn out to be very limited if you store large files in it.

For example, a computer with a standard hard disk drive can store about 10,000 GIFs of your pet dog but may not have enough storage to store even 10 full-length movies about dogs.

Therefore, it is important to know about the file size.

Typically, the common unit of measurement of file sizes is bytes. A byte is typically referred to as the sequence of 8 bits.

A bit is the smallest size of digital information. This is enough for representing a single alphanumeric character and therefore considered as a single unit of information.

In technical terms, a bit is represented either as an ‘on’ or an ‘off’ which the computer CPU processes as ‘1’ for ‘on’ and ‘0’ for ‘off.’

8 bits make 1 byte and it is this byte that is used to pass information in the basic form – its characters.

Any letter or number such as ‘A’, ‘B’ or ‘5’ will be stored in the hard disk of the computer as 1 byte or as 8 bits.

For example, to store the letter ‘R’ the computer uses bytes or 8 bits denoted as ‘01010010’.

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This means that if a document contains 100 characters and is stored in the computer, it will use 800 bits or 100 bytes, excluding any additional data regarding the file that is a part of the file or any other overhead is involved.

At this point, it is important to note for any computer user that there are several non-alphanumeric characters including characters of foreign languages or specific symbols that typically uses multiple bytes.

Based on this measurement, larger files are measured as follows:

  • 1 Kilobyte or 1 KB = 1024 bytes
  • 1 Megabyte or 1 MB = 1024 KB
  • 1 Gigabyte or 1 GB = 1024 MB
  • 1 Terabyte or TB = 1024 GB and
  • 1 Petabyte or PB = 1024 TB.

As said earlier, different files on the computer have different sizes. For example:

  • A short text-only email can be of about 5 KB in size
  • A five-page text document can be about 100 KB in size
  • A standard GIF file of an image of a small dog such as Corgis can be about 834 KB in size
  • Any average webpage can be of about 2 MB in size
  • A MP3 file lasting for 3-minutes can be about 3 MB in size
  • An average CD-ROM comes with a storage space of 700 MB
  • A total of 256 MP3 files can measure up to about 1 GB in size
  • A total of 600 images of high resolution may have a file size of 2 GB
  • Any standard DVD can be of 4.38 GB in size
  • A thousand copies of the Encyclopedia Britannica in total may measure about 1 TB in size and
  • To store 400,000 songs or 900,000,000 photos will take up about 2 TB and 3 TB storage space.

However, if you want to know about file size then the above information is enough to know.

But, if you want to check it out yourself or determine the file size on a regular basis then you will need to know a few more things.

Consider a small text file of 5 letters only, HELLO for example.

Given the fact that a single letter needs 1 byte to store, quite naturally you will calculate and think that the word will take up 5 bytes of space. Simple math!

Well, try it out and then look at the metadata of the file stored to find out the total file size.

You will find that it is a file of 6 bytes and not 5 bytes as you rightfully expected since you have typed only 5 letters – H, E, L, L, and O and every letter needs 1 byte of space.

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Well, the discrepancy is due to the fact that the editor will automatically add a new line to the file which will also need another byte to be represented.

Therefore, representing the entire file in bytes, it will look like this when the binary form is considered:

  • H – 0100 1000
  • E – 0110 0101
  • L – 0110 1100
  • L – 0110 1100
  • O – 0110 1111 and
  • The new line – 0000 1010.

As for the larger files, a much larger space than a couple of bytes will be required to store them in the hard disk.

For example, a standard 400 x 400 image, say of your face, would need as much as 22,096 bytes of hard disk space to store it.

And, a small movie of about 33 seconds would take up a whopping 4,614,170 bytes of space depending on the type.

Usually, to keep things simple, while talking about larger files, larger units are considered to start with, such as a kilobyte.

Considering that, the tentative storage spaces taken up by different files will be as follows:

  • 1 KB of hard disk space will be required to store a 10 x 10 icon
  • 1 MB of hard disk space will be required to store an e-book of 500 pages
  • 1 GB of hard disk space will be required to store a video of 7 minutes long
  • 1 TB of hard disk space will be required to store about 130,000 photos and
  • 1 PB of hard disk space will be required to store about 20 million file cabinets.

You can compare file sizes of different computers easily because the file sizes do not change much from one computer to another.

This is because the computers are quite consistent in their units.

Typically, the file sizes may change depending on whether or not the file is ‘compressed’ and, if it is so, then to what degree it has been compressed.

For example, 1 GB of hard disk space can store an uncompressed video or uncompressed video.

On the other hand, if a video is compressed and is of the same low resolution, the same space in the hard disk can store a 1-hour long video.

Now you may ask, how big is too big for the computer hard disk. Well, it all depends on the context.

What is a File Size


The process to convert file sizes is pretty simple and pretty much similar to converting standard metric system units. Here they are:

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To convert bits to bytes, you will have to divide the number of bits by 8 because one byte is equal to 8 bits.

On the other hand, in order to convert bytes to bits, you simply have to multiply the byte count with 8 for the same reason.

If you want to convert bytes to kilobytes, all you have to do is divide the byte count by 1024, and multiply the kilobyte figure with 1024 to get the number of bytes.

And, if you want to convert kilobytes to megabytes, you will need to divide the kilobyte amount by 1024 and the quotient will give you the value in MB.

Conversely, the MB value needs to be multiplied by 1024 to get the kilobyte value.

Similarly, the process goes on for converting megabyte value to gigabyte value, and the gigabyte value to terabyte value, and the terabyte value to petabyte value.

Therefore, for converting file sizes, you will have to remember three things such as:

  • The byte order such as B, KB, MB, GB TB, and PB
  • The constant value of 1024 and
  • Divide smaller units by 1024 to get larger units and multiply larger units by 1024 to get smaller units.

This means that, if you want to convert byte to gigabyte, you will need to divide the byte value by 1024 three separate times – once to get the kilobyte amount, once to get the megabyte amount, and once to get the final gigabyte amount.


It is very helpful for any computer user to know about the file sizes in detail.

This will help them not only to know how large the file actually is but also identify the limitations of the different storage devices.

That was the whole idea of this article.

About Puja Chatterjee

Puja ChatterjeePuja Chatterjee is a technical writer with extensive knowledge about computers. She graduated from BIMS. Her expertise includes technology writing and client relationship management gained through over 12 years of experience. Follow Her at Linkedin.