How to Free Change Block Size from 4K to 64K?

This post is about how to change block size from 4K to 64k. Three free tools will be introduced to change cluster size from 4K to 64K on Windows 11, 10, 8, 7.


By Cherry / Updated on October 27, 2023

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About block size and cluster size

According to Wikipedia, in computing, a block is the size of a block in data storage and file system. Block, sometimes called a physical record, is a sequence of bytes or bits, usually contains some whole number of records, having maximum length, a block size. Block size, the minimal unit of data for block ciphers. In modern cryptography, symmetric key ciphers are generally divided into stream ciphers and block ciphers. Block ciphers operate on a fixed length string of bits. The length of this bit string is the block size.

When operating system read and write files, it will read and write according to the cluster size of file system. The file system is generally based on Cluster size, sometimes called Block size to read and write data. This Cluster is generally the smallest 4K, and the large size is 32K, 64K, which is depending on the application. For example, the application of Oracle is generally used in 4K or 8K Block size, and large file read-write can be used with 128K or even 256K.

Why change block size from 4K to 64K?

At the very first, the 512 bytes cluster is the standard. With the develop of technology, the 4K is common now. And the 64K is for big file storage like game, 3D movie, HD photo. You will benefit from the 64K cluster size. For example, games like warcraft, overwatch, install package are big, the large cluster size like 64K will significantly improve its performance.

How to change block size from 4KB to 64KB?

But how to change block/cluster size from 4KB to 64KB? Here we provides you the best three ways to do it.

*** If you do not want to lose any data on the partition, you should copy partition for backup in advanced.

1. Change cluster size in Windows File Explorer

You can try to use Windows File Explorer to change block/cluster size by formatting partition.

1. Press Win + E to open Windows Explorer. Right-click the partition which you want to change the block/cluster size, select Format... (Format partition will delete all data on the partition, please make sure you have already backed up the data on partition).

2. In the format dialog, click Allocate unit size, select 64 kilobytes, and select Quick Format, and click on Start.

Unit Size

3. Wait till the progress done.

2. Change cluster size from 4K to 64K with command prompt

You can also change block size from 4K to 64k with command prompt. Of you do not know how to do it, follow the guides below:

1. Click Start, type cmd in the search box, and then, run the command prompt as administrator.

2. Then, you can type the following command in order (each command will be executed by pressing Enter).


•list disk

•select disk n (n refers the disk number that the partition which you want to change cluster size on)

•list partition

•select partition m (m refers the partition number that you want to change cluster size)

•format fs=ntfs quick unit=64k


Cluster Size

2. Chang block size from 4K to 64K with AOMEI Partition Assistant

Using a third party software to change block/cluster size from 4K to 64K should be the easiest way. AOMEI Partition Assistant Standard is such an easy-to-use freeware that can help you format partition to change cluster size from 4K to 64K without losing data.

Step 1. Free download AOMEI Partition Assistant Standard, install and launch it. If you do not want to lose data, you can use copy partition wizard to copy the partition first.

Download FreewareWin 11/10/8.1/8/7/XP
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Step 2. The, you can format partition with AOMEI Partition Assistant to change cluster size from 4K to 64K. Right click the partition, select Format Partition.

Format Partition of 30GB USB

Step 3. In the format partition window, you can change cluster size in the drop-down menu, here you can choose 64KB to change cluster size from 4KB to 64KB. Click OK.

Specify Cluster Size 30GB

Step 4. Here you will back to the main interface, click Apply at the toolbar and then click Proceed to execute the whole operation.

Wait till the progress reaches 100%. Close the program to quit it.


Those three methods all can help you change block size from 4K to 64K. But we highly recommend the software AOMEI Partition Assistant, the great partition manager, can not only help you change cluster size from 4KB to 64KB, but also can help change file system between NTFS and FAT32 without reformatting, convert MBR and GPT without deleting partition, change partition ID, etc. Besides, you can upgrade to AOMEI Partition Assistant Professional to get more advanced features, for example, if you use an SSD, it supports you to do 4K partition alignment which can optimize its performance or create portable Windows 11 USB. Besides, its data recovery feature is welcomed by lots of users.

Cherry · Staff Editor
Cherry is an editor of AOMEI Technology, she covers backup & restore, hard disk & partitions management, cloud files transfer, website & database backup and so on for AOMEI. She enjoys helping people find solutions to their problems. She loves traveling, cooking, reading and so on. She takes most of time with her family when she is not working.