what is size on disk?

[ShawnD1]

if you click properties on a file, you will notice it has 2 size things: "size" and "size on disk"
the size on disk value is almost always slightly bigger than the size. what does 'size on disk' actually mean then?

[Comage]

Size is the actual size of the file. Size on disk includes wasted space (depends on your cluster size). The smaller your cluster size, the less wasted space there'd be.

[omega31]

"Size on disk" is the actual space taken on the disk, including wasted, or unused, space. It is always a multiple of the size of your clusters.