Size vs size on disk

Size vs size on disk

Size vs size on disk, what are the differences between both? This article explains it all! When looking at a folder’s properties on your computer, you will notice different options.

Under the “General” tab, you can see two separate parameters explaining the size of that particular folder.

“Size” and “Size on Disk” are two different terms to define the file or folder size in your computer.

Sometimes you will find that both numbers are quite different for some files and folders on your PC. In this article, we will explain everything you need to know about this matter.

Storage in a computer happens in different clusters of your hard drive. Clusters are groups of disk sectors inside your hard drive where the data gets recorded.

Size on disk describes the amount of cluster allocation a file is using. In contrast, file size refers to the actual size of the file in bytes.

Size vs size on disk: Why is there a difference between both?

Size vs size on disk

The hard disk is made of tracks and sectors. Windows allocates space for files in different clusters. The size of a cluster can change, but some values for cluster size range from 512 bytes to 32KB or more.

The allocation unit size in your hard disk drive will determine how much space your operating system will give to a folder or file to store.

An allocation unit is a group of sectors reserved on the computer hard drive for storage. If the file you want to store, takes up only a portion of the allocation unit, the whole allocation unit will be used.

The operating system will always give the minimum possible space for storing a file.

For instance, if the allocation unit is 32KB, then it does not matter if the file size is 2KB, 10KB, or 20KB. The operating system will “allot” 32KB for that particular file.

Let us consider another example: if the allocation unit is 4096 bytes in your hard disk drive, then it denotes that Windows will give 4096 bytes of storage space for any file having a size between 1 byte and 4096 bytes.

It means that if you have a file that has an actual size of 2000 bytes, it will still take 4096 bytes on your hard disk.

The reason for the larger size occupancy is that the allocation unit is 4096 on your computer’s hard disk. One file can take one allocation unit, and other files cannot share it.

Can this be an issue while moving files between drives?

In one word: no. Moving files from one drive to another will not cause any problems. The amount of data that you are moving will stay the same.

If you have space available in the new drive, you will be able to transfer the data quickly.

However, if some files in your data are more significant in size than the maximum allocation unit, then you may face problems.

For example, if you have a USB flash drive offering 32GB capacity and it is in the FAT32 system, then you cannot move any file having a size greater than 4GB.

If you try to copy a file bigger than 4GB in size to that particular flash disk, the system will return an error message stating you do not have enough space available. Even though you might have all the 32GB free, you will not be able to transfer the file successfully.

Wrap Up

Size and size on disk are different terminologies that describe the size of a file on your computer.

Size refers to the actual size of a file, while size on a disk relates to the amount of storage a particular file is taking on your hard disk drive.

The amount of storage space required for a specific file depends on the allocation unit of your computer’s hard disk drive.

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