Question: How much space is lost due to formatting and why? Answer: Just like a floppy, we need to write a File Structure to the CDRW disc to allow files to be copied or erased on the disc. 700 MB 12cm CDRW disc has the formatted capacity of 574 Mbytes. 650 MB 12cm CDRW disc has the formatted capacity of 536 Mbytes. 200 MB 8cm CDRW disc has the formatted capacity of 163 Mbytes.