# How to calculate FAT32 partition?



## PHM (Oct 7, 2005)

Each section of cluster is 4K under 8G patition, what about 32G or bigger?


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## lotuseclat79 (Sep 12, 2003)

PHM said:


> Each section of cluster is 4K under 8G patition, what about 32G or bigger?


Hi PHM,

Here is a table of FAT32 Cluster sizes from Upgrading and Repairing Pcs by Scott Mueller, 10th Ed:

Partitions Size/Cluster Size
------------------------------------
0M to less than 260M/512 bytes
260M-8G/4096 bytes
6-16G/8,192 bytes <---- Actual entry in book. I assume it should be: 8-16G
16-32G/16,384 bytes
32G-2T/32,768 bytes

With regard to calculating the size of a FAT32 partition, here is an example:
Using smaller clusters reduces wasted disk space caused by slack. The same 2G partition with 5,000 files on it would use 4K clusters with FAT32 instead of 32K clusters with FAT16. Assuming the same amount of slack for each file, the smaller cluster size reduces the wasted space on that partition from over 78M to under 10M. Using smaller clusters means that there must be many more of them, and more entries in the FAT as well. A 2G partition using FAT32 requires 524,288 FAT entries, whilethe same drive needs only 65,536 entries using FAT16. Thus, the size of one copy of the FAT16 table is 128K (65,536 entries * 16 bits = 1,048,576 bits/8 = 131,072 bytes/1,024 = 128K), while the FAT32 table is 2M in size.

-- Tom


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