About this interactive
Your operating system saves a file into clusters, the small fixed-size compartments a drive is divided into, and records which clusters the file uses in a table. A cluster belongs to one file at a time, so a file always takes whole clusters.
The rule: divide the file's size by the cluster size and round UP to a whole number. That is how many clusters the file takes. Multiply it by the cluster size and you have its size on disk.
The lesson's example: a text file of 2,280 bytes on a drive with 4,096-byte clusters fits in one cluster, so its size on disk is 4,096 bytes. A file of 4,097 bytes is one byte too big for one cluster and takes two: 8,192 bytes on disk.
The space left over in a file's last cluster is wasted, which is why a drive full of small files does better with smaller clusters. Windows calls the cluster size the allocation unit size when you format a drive.
One exception you will not meet here: on NTFS, a very small file (under about 700 bytes) can be stored inside the master file table itself and use no cluster at all. Every file in this activity is big enough to need clusters.
Type numbers only. Commas are fine: 8,192 and 8192 are both accepted.
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