File Sizes Explained and File Size Convertor

Explanation of file sizes when using Windows 7, 8, Vista and XP. File size convertor for bytes, Kbs, Mbs and Gbs

Why are File Sizes Important

Having some knowledge of file sizes is useful in your computer activites as the size of files will determine:
1. How quickly your hard drive will fill up as you save your work.
2. What speed your computer can work at with open programs.
3. How quickly you can download data such as music, movie and pdf
files from the internet or send data such as as emails.


When you buy a computer, the specification may say it has a 160gb (160 Gigabyte) hardrive. This means you can store files,programs and your computers operating system within that limit. It follows that what you store has a size and files and programs etc have a size which is denoted in the form of a number (size) and then usually 2 letters as shown in the hardrive example above (160gb).

The Sizes

The sizes of files and other elements used and stored on your computer are measured in bits and bytes.

A Bit is the smallest unit of data that a computer uses.

The sizes are:

· 1 Bit = Binary Digit
· 8 Bits = 1 Byte
· 1000 Bytes = 1 Kilobyte (kb)
· 1000 Kilobytes = 1 Megabyte (mg)
· 1000 Megabytes = 1 Gigabyte (gb)
· 1000 Gigabytes = 1 Terabyte (tb)
· 1000 Terabytes = 1 Petabyte (pb)
· 1000 Petabytes = 1 Exabyte (eb)
· 1000 Exabytes = 1 Zettabyte (zb)
· 1000 Zettabytes = 1 Yottabyte (yb)
· 1000 Yottabytes = 1 Brontobyte (bb)

Convertor at bottom of page.

A Kilobyte is actually 1024 bytes but most computer users and manufacturers notate it as 1000 as above.

file size in Windows Explorer

Some examples of File Sizes

1. If you create a text document (extension .doc) in Microsoft Word with no images or clip art, the size may only be in the region of 12kb to 40kb.

2. If you designed a graphic image in Microsoft Paint or Photoshop (extension .gif - .jpeg - .bmp - .psd) the file size increases and could reach a hundred or more Kilobytes (kb).

3. Insert a graphic image into a word document (clip art - photo) and the file size obviously increases.

4. If you download a photograph ( .jpeg) from your digital camera onto your computer it's file size could be heading towards 1000kb which would make it 1 megabyte (1mg).

5. Create a PDF document in Adobe Acrobat and you get file sizes of 100kb to 500kb (again even more with a lot of graphics in the document).

6. Begin working with video/movie files or download them from the internet ( .avi - .mov - .wmv ) and the size rockets because so much data is needed to create the file ( imagine it as a photograph changing frame by frame that needs to be stored to make the file). File sizes start reaching  1/2/3/4/5gb according to the length and quality of the video. When downloading these large files it helps when they are split into smaller packages with file extensions such as .rar. These files then need extracting to make then usable on your computer ( use the program Winrar for .rar extensions).

From the above you can see that on a computer used at home a 160GB hardrive would be very difficult to fill with just Microsoft Word documents but could be filled quite easily with perhaps a hundred movies.


Remember when emailing that the speed of transfer of data over the internet between two computers is reliant on "bandwith". This bandwith transfers small files better than large ones. Emailing a large photograph to someone may fail if the bandwidth between the two computers struggles with the amount of data  being transferred in one file/email.

File Sizes and Computer Memory (RAM).

If your computer has 1GB of memory ( RAM - Random Access Memory ) it will be able to operate smoothly running more open programs than if it only has 500MB. Overloading a computers memory by trying to open and run too many programs leads to your commands working slower and instability leading to a possible crash ( computer locks up and becomes unusable without a restart).

File sizes affect the above because programs use the memory during the manipulation and creation of files saved on your computer.

1. If you only have MS Word open and you are just creating a text document your computer will function with very little memory (RAM). The entering of text and it's manipulation puts little demand on the memory.

2. If you are designing a graphic in an image editing program like Photoshop you are manipulating coloured pixels,vectors and shapes of different sizes to produce the finished graphic. This makes a large file size as the program has to store in the file the data to allow the file to be opened or inserted into another program and appear as first created and saved. Programs like Photoshop put more demand on the memory allowing fewer programs to be open and working smoothly on your computer at one time..

3. If you have a few programs open and then decide to play a video/movie file in Windows Media Player you may find the video stuttering or stopping. This is because video/movie files are very large and the memory cannot cope with the extra amount of data needing to be processed in the video file.

The more memory (RAM) the better applies to computers.

Downloading from the Internet

A music track ( .mp3 music file size 2mb upwards) will take a lot less time to download than a movie ( .avi movie file size 700mb upwards). The bigger the file the slower the download.

The File Storing Capacity of Portable Media used to Save Files or Swap Files (data) Between Computers.

Memory Sticks/USB Flash Drives - 8  gigabytes (gb)
3 1/4" Floppy - 1.44 Megabytes (mb) - Memory Sticks ( inserted in USB port ) have superceded Floppy Disks.
CD - 700 - 800 Megabytes (mb) - good for music compilations.
DVD - 4.7 Gigabytes (gb) - good for storing and playback of a movie.

Exact File Size Conversion
Bit Smallest unit of measurement.
Byte 8 bits
Kilobyte (KB) 1024 bytes.
MegaByte (MB) 1024 kilobytes (KB)
GigaByte (GB) 1024 megabytes (MB)
To convert these in exact figures, it is best to use a calculator designed for this purpose.

Fize Size Convertor

JavaScript Kit

Books & Manuals

ECDL - European Computer Driving Licence

Buying a Computer

MS Word

MS Excel

Windows 7

Windows Vista

Windows XP

Powerpoint 2003/2007


Dreamweaver CS4/3/MX

Web Design - Publishing


Adobe Acrobat

Adobe CS4/CS3/CS2

Adobe Photoshop

Adobe Flash

Build Your Own PC

Digital Photograhy

Internet Security

Link to this page for everyone's benefit if you found it useful

© IT Buddy 2016