know What is the difference between size and size on disk
What is the difference between “size” and “size on disk”? I will be assuming that you are using the FAT/FAT32 filesystem here, since you mention this is a SD card. NTFS and exFAT behave similarly with regards to allocation units. Other filesystems might be different, but they aren't supported on Windows anyway. If you have a lot of small files, this is certainly possible. Consider this: 50,000 files. 32 kB cluster size (allocation units), which is the max for FAT32 Ok, now the minimum space taken is 50,000 * 32,000 = 1.6 GB (using SI prefixes, not binary, to simplify the maths). The space each file takes on the disk is always a multiple of the allocation unit size - and here we're assuming each file is actually small enough to fit within a single unit, with some (wasted) space left over. If each file averaged 2 kB, you'd get about 100 MB total - but you're also wasting 15x that (30 kB per file) on average due to the allocation unit size. In-depth explanation W...