Which Is the Best NTFS Allocation Unit Size, How to Set?

Sherly updated on Feb 27, 2023 | Home >Computer Instruction

To know the answers to these questions above, you must read this article. So let's get straight to it!

What Means NTFS Allocation Unit Size

The size of your allocation unit will be equal to the size of an empty file. If you have several small files but a large allocation size, every file on your drive will need to be at least this huge, which could consume a lot of space on your hard drive. To utilize an extreme example, in case you possess 1MB NTFS allocation size and 10 8KB files, each of them will consume 1MB. 10MB would be the entire drive space, not 80KB. Therefore, it can be seen that it's enough squandered space!

Usually, 4 Kilobytes is the most common NTFS allocation unit size nowadays. When you keep your allocation unit size small, a higher allocation time will be required, leading to a slower PC. However, it will take maximum disk space if it's too big. 

ntfs allocation unit size

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What Is the Best NTFS Allocation Unit Size

You must remember that if you fall under Microsoft's definition of a "Standard User," you should stick with the default 4096 bytes. However, the default criterion could be changed based on what you use them for in different partitions.

NTFS Allocation Unit Size for Movies:

You might select the 2MB maximum allocation unit size, but remember that this will result in smaller files (such as subtitle files) using the bare minimum of that space.

NTFS Allocation Unit Size for Images:

On the other hand, if you have a devoted drive to images and music, it might change things; for example, the music and image files are smaller than the movies. Hence, you may aim to keep the size of your allocation units below the size of your audio and video files.

How to Set NTFS Allocation Unit Size

While setting the NTFS allocation unit size, you must scan the given partition or drive and understand what's ideal for that particular one. In case it seems doubtful, you may leave it as the default. However, two possible ways are the following to change and reset the NTFS allocation unit size:

Method 1. Change NTFS Allocation Unit Size with EaseUS Partition Master

Do you know with the support of a professional partition manager, you can change the NTFS allocation unit size? That top-notch software is EaseUS Partition Master Free, an all-in-one free tool designed for every user.

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Step 1. Right-click the partition that you need to change its cluster size, select "Advanced" and click "Change Cluster Size".

Right-click to change cluster size

Step 2. Click the size list below the New size section, and select a desired cluster size you want to adjust for the disk partition, click "OK".

Adjust cluster size

Step 3. Click "Execute 1 Task(s)" and click "Apply" to confirm the operation.

confirm the opreation

When you're bored of copying and pasting things, EaseUS helps imitate or clone partitions from one hard disk to another without risking data loss on your disk partition. The best features of EaseUS Partition Master are given below:

  • Create or Remove a partition: All data on the drive is saved after creating any necessary partitions or deleting any unnecessary partitions. 
  • Move or Resize the partition: Without any data loss, you can easily alter the used partition space (s): Move or Resize to alter disc space willingly.
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Method 2. Change NTFS Allocation Unit Size with CMD

You may use the CMD command prompt to alter the NTFS allocation unit size for videos and games. Follow the steps below to change the NTFS allocation unit size with diskpart commands in CMD:

Step 1: To launch the run, hit window + R.

Step 2: To access the ongoing command prompt as the administrator, type the command "CMD" and hit Ctrl + Shift + Enter.

Step 3: Hit "Enter" to open Diskpart.exe after entering the diskpart.

Step 4: Type the below-mentioned command, and keep pressing enter:

  • list disk
  • choose disk * (the target disc or partition's number is indicated by the *)
  • list division
  • choose a partition
  • format fs=ntfs unit=64k

format fs commands


After skimming through this article, you must have understood what NTFS allocation unit size is and how to set one with the help of two methods. What's more? You can easily complete this task using third-party software or a built-in Windows application.

Regarding EaseUS Partition, it cannot only modify cluster size without costing consumers anything, but it can also repartition hard drives and convert FAT32 to NTFS and NTFS to FAT32 without formatting or losing data, among other disc partitioning-related tasks.

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FAQ About NTFS Allocation Unit Size

The FAQs about NTFS Allocation Unit Size are given below to comprehend the topic better. If you have further problems, continue to read.

1. Does allocation unit size affect speed?

Yes. If the allocation unit size is too small, it may reduce your PC's speed. Moreover, allocation might take longer when more allocation units are assigned to every file. However, if you make the allocation unit size too much, it will consume valuable disk space.

2. What allocation unit size should I use for the NTFS flash drive?

In case the size of your flash drive is bigger than 16GB, the most appropriate allocation unit size must be 16KB. However, the default cluster size for NTFS drives is 4KB for 7MB - 512MB, 512MB - 1GB, 1GB - 2GB, and 2GB - 2TB.

3. What will happen if the allocation unit size is large?

When you have different small files, it would be an amazing idea to maintain a minimum allocation size so that your hard drive space will stay manageable. On the other hand, when you possess several larger files, keeping the allocation size higher will boost the system's performance because there will be fewer blocks to aim for. However, if the allocation size is extremely big, it will consume the maximum of your PC's disk space.

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Updated by Sherly

Sherly joined EaseUS in 2022 and she has always loved writing articles and enjoys the fun they bring. She receives professional training here, focusing on product performance and other relative knowledge.

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