Why Does The Size Of A File Vary From Its Size On A Disk

Many say that the difference between size and size on disk is big, but why is this the case?

People get confused when they look at the properties of a folder, file, or drive and see that the property's size and the size on the disk are different. On the properties page, the size of the file is shown in its actual size.

On the other hand, a file's size on the disk tells you how many bytes it takes up on a hard drive. Most of the time, these values are very close to each other. You will see the conflict if you open the properties of a folder or file.

Here, we'll discuss why this difference exists and if it should worry you.

Size vs Size on Disk

When you understand the main idea of both terms, you can see that they are very different.

What does "file size" mean?

When you click on a file or folder's properties, you can see its bytes and size. This value tells you how many bytes and how big the file is. The file size is used to figure out how much data is in the storage device. The size of this thing is shown as a byte.

What does "file size on disk" mean?

How much area a file takes up on the hard disk drive is shown by its size on the disk. When a file is put into a modern storage device, it usually takes up a little more space than the file itself. That's why the difference between size and size on disk is clear. Check out the picture below; it will help you understand the basics.

Why do Size and Size on Disk mean different things?

Now, we want to know what factors affect the size of this file on disk. It depends on how your file system stores files on the storage drive. Each file has its address, and to save space, the file system treats all files as if they were in the same cluster. The maximum size of a file and the number of bits set aside for the file size information affect the size of a file's capacity. For example, the FAT32 file system can handle files up to 4,294,967,295 bytes in size.

Most of the time, the sizes of NFTS clusters range from 512 bytes to 64 KB. No matter how small the file is, it takes up a certain number of collections when written to the hard drive. For example, if a file is 1 KB and you save it in a file system with 2 KB clusters, it will take up 2 KB of space on the disk.

When you save the 1 KB file in a file system with 32 KB clusters, it will take up 32 KB of space on the disk. Now, it's clear that the size of a file on a disk will be bigger than the size of the file itself. You may also be surprised sometimes, but that will be a rare case.

For example, you may run into a situation in which the size of the file on the disk is smaller or the same as the size of the file itself. Remember, this will only happen when you use your operating system's automatic compression feature. This feature shrinks the file so that it takes up less space on the disk than it does.

There isn't a big difference between the actual file size and the size on disk, but many users have said there is a big difference between the actual file size and the size on disk. So, let's figure out why there is such a big gap between the two.

Why is the difference between Size and Size on Disk so significant?

There are sectors and tracks on a hard drive. If you use a Windows PC, the operating system gives cluster units space on your hard drive. Your storage drive's file system sets different cluster sizes, changing the disk's amount of space. When there is a significant variation between size and size on disk, you can check to see if the folder contains many small files and if the cluster size is big.

This difference will get more prominent as the number of files grows because each file takes up space on the hard drive. This size of wasted drive space keeps increasing until it reaches a certain level, at which point the size of the disk will be much bigger than the actual size.

These things can happen when there are many small files in a folder. In addition, the amount of space on the disk also depends on the size of the clusters in your file system. When you set the cluster size for the disk to be bigger and have many files, you will waste more space. The average size of a cluster on a drive is 4 KB. You can choose either 32 or 64 KB cluster size for large files like games and 3D movies.

How do make the difference between Size and Size on Disk less noticeable?

You can get the most out of your storage devices when you manage the cluster size well. You can change the disk's cluster size if you want to reduce this big difference. You can change the cluster or allocation unit size with built-in Windows tools like Diskpart and Disk Management. These tools can help narrow the difference between sizes in a big way.

People get confused when they see a difference in size on a disk. It's because there are so many small files and the clusters are so big. Most of the time, the disk size is much bigger than the file size itself. Also, if your operating system uses an auto-compression system, this size might be smaller than the actual file size in some cases. You can do this by using the tools that are already built-in. These tools make a partition and significantly reduce the size of allocation units and clusters.