[FAT32 Partition Size Guide] What Allocation Unit Size Should I Use for FAT32?

Updated by the following author

Tracy King 

Last updated on April 22, 2024

When you buy a new USB flash drive or SD card, you probably don't think about formatting it. But formatting a flash drive is actually a smart and necessary process. In short, there are two main benefits to formatting a USB flash drive or SD card. First, it prepares the drive for proper use on your computer. Second, it creates a file system that organizes your data and lets you store as many files as possible.

When formatting a flash drive, you need to choose the right allocation unit size, also called cluster size. Different file systems have different allocation unit sizes, and in this article, we'll tell you what allocation unit size to choose for FAT32.

Page Content:

1. 1. How to Check Allocation Unit Size
2. 2. What Allocation Unit Size to Use for FAT32
3. 3. Bonus Tip: How to Convert FAT32 to NTFS with Partition Manager Tools

How do I check the allocation unit size?

Allocation Unit Size, also referred to as Cluster Size, is the block size on a hard drive when formatting with FAT32, exFAT, or NTFS file systems. The hard drive is divided into multiple clusters, and the Allocation Unit Size denotes the size of a single cluster. The file system in use when formatting the partition keeps track of these clusters. When a file or part of a file is written to any cluster, that cluster is considered occupied.

To check the allocation unit size of a USB drive or SD card, follow these steps:

Step 1: Plug the flash drive into your computer. Open File Explorer.

Step 2. Right-click on your USB drive and select "Format."

Step 3. The current allocation unit size of the disk is shown under the Allocation Unit Size dropdown.

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See Allocation Unit Size for FAT32: What Allocation Unit Size Should I Use for FAT32?

Sometimes, users need to convert the file system of USB flash drive from NTFS to FAT32 or FAT32 to NTFS. Changing the file system of a disk means that you should also change the allocation unit size. But what is the appropriate allocation unit size for FAT32? Don't worry, we will tell you the answer.

The allocation unit size depends on both your file system and the size of your USB flash drive or SD card. For a FAT32 drive, the default cluster size in Windows 10 is as follows.

A KB is 1024 bytes. Typically, common USB flash drives are larger than 2 GB. If your USB drive is less than 8 GB, the most suitable allocation unit size is 4096 bytes. If the drive is between 8 GB and 16 GB, the ideal allocation unit size is 8192 bytes. If the drive is greater than 16 GB, the appropriate allocation unit size is 16 KB.

For NTFS drives, the default cluster size in Windows 10 is as follows.

Extra Tip: How to Convert FAT32 to NTFS with Free Partition Manager

FAT32, exFAT, and NTFS are file systems used in the Windows operating system. A file system provides a way to organize a drive. It dictates how data is stored on the drive and what types of information can be attached to a file, such as filenames, permissions, and other attributes.

Among these three file systems, NTFS is the most modern. It is more efficient and supports many features. Therefore, in some cases, users may need to format a flash drive from the old FAT32 to the newer NTFS. To carry out this process, we would like to introduce you to a free tool - AOMEI Partition Assistant Free.

This free tool is for partition management. You can use it to resize and move partition, solve low disk space problem on C drive, convert FAT32 to NTFS, as well as merge partitions. Now, please click the button below to download Partition Master Free, and then follow the guide to learn how to convert FAT32 to NTFS.

Step 1: Install and run Partition Master on your computer.

Step 2. In the Disk Manager, right-click on a FAT32 partition and select Advanced, then Convert to FAT.

<Step 3> Click "Proceed" in the dialog box that appears.

Step 4: Click on the “Convert” button to start the process and wait for it to complete.

For more information about cluster sizes, such as the best SSD cluster size, see the following article:

What Is the Best SSD Allocation Unit Size in Windows 11/10

On this page, we will introduce what is the best SSD allocation unit size in Windows 11/10. You can also find the best solution to change it.

Bottom line

This article should answer all your questions about “What allocation unit size to choose for FAT32.” Normally, the allocation unit size for a FAT32 drive ranges from 4KB to 16KB. You can refer to the table in the article for reference. Also, if you're interested in converting FAT32 to NTFS, try the tool Partition Master Free.

Allocation Unit Size for FAT32 in PAA

What should the allocation unit size be for a FAT32 32GB?

For a 32 GB flash drive formatted as FAT32, the allocation unit size can be set to 16 KB.

What is the best cluster size for FAT32?

For FAT32, the ideal cluster size depends on the hard drive and the purpose of the partition. In simple terms, a cluster is a group of sectors with a minimum and maximum number of bytes that make up a File Allocation Table (FAT) allocation unit. Generally, smaller cluster sizes mean more efficient use of hard drive space. For FAT32, the optimal cluster size for most systems by default is 4KB (4096 bytes). Some systems might be able to use an optimal cluster size of 16KB or 32KB for larger partitions.

What allocation unit size should I use?

If you're a beginner, the default 4096 bytes is a standard allocation unit size.

【What is the allocation unit size for a 32GB SD card?】

The allocation unit size for a 32 GB SD card can vary quite a bit depending on the card type and how it's formatted, but it's usually between 16 KB and 32 KB.