With FAT16 the maximum partition size is 2GB when your maximum cluster size is 32K.

This is calculated by multiplying the number of addressable units by the cluster size.

(2

^{16}Allocation units) * (2^{15}bytes/cluster) = 2 GiB

However with FAT32, when I do the same calculation I get a much larger number than the 8 TiB maximum when using 2^{32} clusters.

(2

^{32}Allocation units) * (cluster size)

If I use a cluster size of 512 bytes, I've already arrived at 2 TiB.

In an XP TechNet article, Microsoft says

The maximum possible number of clusters on a FAT32 volume is 268,435,445, and there is a maximum of 32 KB per cluster, along with the space required for the file allocation table (FAT).

This puts the maximum cluster size at 2^{28} - 11.

Why is the maximum number of clusters in FAT32 2^{28}-11 and not 2^{32}, given that it was 2^{16} in FAT16?