TABLE 2: FAT32 Cluster/Allocation Unit Size by Volume Size
Volume-Size Range	Default Cluster (Allocation Unit) Size
512MB to 8191MB*	4KB
8192MB to 16,383MB	8KB
16,384MB to 32,767MB	16KB
32,768MB or larger	32KB
*FAT32 doesn't support volume sizes smaller than 512MB.