Comparison of FAT16 and FAT32 File Systems
By Mike Angelo – 22 March 98 ©

Webmaster's Note: 

This article was written just for the online edition of About Computers specifically to supplement our article Windows 98 - The Changing View of the Information Highway. We urge you to read also that article. 

The PartitionMagic Development Team contributed to this article. 

For an explanation of the effects of partition and cluster sizes on wasted hard drive space please see our article "Use Magic to take Command of your System and Hard Drives". 

DOS and Windows 3.x use the FAT16 (File Allocation Table) file system. Windows 95 OSR2 and Windows 98 can use Microsoft's new FAT32 file system. FAT32 allows hard drive partition sizes greater than 2-GB. It also makes more efficient use of hard drive space than does FAT16 on partitions larger than 512-MB. 

Table 1 below shows the minimum cluster sizes for different partition sizes for both FAT16 and FAT32 formats. The wasted space entries are estimates. The actual space waste realized on a particular system depends on the actual mix of file types and sizes specific to the hard drive. 

Where hard drive partition sizes range from 512-MB to 4095-MB the FAT32 system can provide a 21% to 46% reduction in estimated space waste. FAT file system comparisons are not applicable for partition sizes less than 512-MB because smaller partitions cannot be formatted to the FAT32 system. 

Windows 98 includes a utility to convert FAT16 partitions to FAT32 partitions. However, the Windows 98 utility is a one-way process. You will not be able to convert the FAT32 partitions back to FAT16 partitions. However, Partition Magic version 3.x can convert FAT32 to FAT16 and FAT16 to FAT32 partitions. 

Once you convert your partition to FAT32, the only operating systems that will be able to read and to write to your FAT32 partitions are Windows 95 OSR2 and Windows 98.

Table 1. Comparison of Cluster Sizes and Wasted Hard Drive Space for FAT16 & FAT32 Partition Sizes Up to Four GB.
 Drive Partition Size FAT16  

Cluster Size

Typical % Wasted Space Fat32  

Cluster Size

Typical % Wasted Space FAT32 Waste Reduction
16 MB–32 MB 512 bytes * * * *
32 MB–64 MB 1K * * * *
64 MB–127 MB 2K 2% * * *
128 MB–255 MB 4K 4% * * *
256 MB–511 MB 8K 10% * * *
512 MB–1023 MB 16K 25% 4K 4% 21%
1024 MB–2047 MB 32K 40% 4K 4% 36%
2048 MB–4095 MB ** 64K 50% 4K 4% 46%
4096 MB–8 GB * * 4K 4% *
8 GB–16 GB * * 8K 10% *
16 GB–32 GB * * 16K 25% *
More than 32 GB * * 32K 40% *
1). FAT32 Partitions must be at least 512 MB.

2). Based on data from A Guide to Reviewing and Evaluating Windows 98 Beta 3, p. 26, Microsoft Corporation, 1998, Partition Magic 3.0 User Guide, p.147, PowerQuest Corporation, 1996, and Partition Magic 2.0 User Guide, p.19, PowerQuest Corporation, 1996.

3). * Indicates not applicable or data not available.

4). ** This FAT16 partition size is available on Windows NT and not on DOS or other Windows versions.

4). Wasted space entries are based on estimates contained in PowerQuest documents.

5). FAT12 is used with partitions less than 16-MB. The cluster size there is 4-KB.

At this time FAT32 is not compatible with other operating systems such as Linux, Unix, Windows NT, DOS, pre-Windows 95 OSR2, and so forth. Red Hat Software is expected to have a solution for the FAT32-Linux compatibility problem by the end of May, 1998. Please see our article Windows 98 - The Changing View of the Information Highway for FAT 32 compatibility issues.
Make sure that any disk, partition, and file management utilities such as defraggers and file repair applications you run on a FAT32 partition are compatible with FAT32. If not you could really mess things up.

We discussed these FAT issues with the PartitionMagic Development Team. Regarding use of a 64-KB cluster size in FAT16 they note:  "This cluster size is only available when running WindowsNT.  So for Windows95 users, this is not available and the maximum partition size is 2,040MB."

"We use a maximum size of 2,040-MB rather than 2,048-MB in our documents.  This is because OS/2 does not support more than 65,278 clusters rather than the 65,525 clusters that MS-DOS supports.  We have kept this slight change in {our stated} limits for compatibility."

"FAT16 partitions have a maximum of 1,024 root directory entries (512 entries is normally used with newly formatted partitions).  With the advent of long file names, these root directory entries can fill up quickly.  FAT32 circumvents this problem by treating the root directory as any other directory and allowing it to grow.  This can be a concern when converting from FAT32 to FAT16."

"FAT32 partitions have a larger FAT size since each entry uses 4 bytes rather than the 2 bytes used by a FAT16 FAT entry.  On a 4-GB partition the FAT can be as large as 4-MB (per copy of the FAT) compared to 130-KB per FAT maximum in a FAT16 system."

"Regarding the FAT12 issue, FDISK will create a FAT12 partition if the specified partition size is less than 16-MB because it produces a smaller FAT, and that was the standard file system until FAT16 came along.  We guess that was done for efficiency and compatibility."

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For more detailed information about FAT32 features, compatibility considerations, performance, use in multi-boots systems, creating FAT32 partitions, and technical implementations, please check Microsoft's  FAT32 File System Market Bulletin.

For more information about Windows 98 please check our article Windows 98 - The Changing View of the Information Highway  and also please check the Windows 98 Beta 3 Web site. For more information about obtaining a preview copy of Windows 98 check the Windows 98 Preview Web site.

For more information about Partition Magic, please check the PowerQuest Web site.

For more information about Red Hat Linux please check the Red Hat Web site.

(Note: We have been experiencing difficulties pulling in some Web pages from the Microsoft Web site. Also, when we do manage to pull in the Microsoft Web pages, we have noticed they sometime cause memory/resources leaks. We suspect this is due to some incompatibility between some HTML, JAVA code, or whatever Microsoft uses for its Web site and some Web browsers.)

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