How Much Information Can a CD Hold?

When you copy data to a CD, you must make sure that your data does not exceed the capacity of the CD you are recording to. Due to the audio origin of CDs, the amount of information a CD can hold is measured in minutes:seconds:sectors. Each second contains 75 sectors, each of which can hold 2048 bytes (2 kilobytes) of Mode 1 user data. Recordable CDs come in 21-(80 mm diameter), 63-, and 74-minute sizes (both 120 mm diameter), which can contain.

21 min x (60 sec) x (75 sectors) x (2 kilobytes) = 189,000 kilobytes = 184 megabytes

63 min x (60 sec) x (75 sectors) x (2 kilobytes) = 567,000 kilobytes = 553 megabytes

74 min x (60 sec) x (75 sectors) x (2 kilobytes) = 660,000 kilobytes = 650 megabytes

Using the CD Size command in the Edit menu, you can set the capacity of the CD you want to produce so that you don't exceed it. The status bar shows you how much space is used, how much space is still free, and the percentages of each.

Files on CD do not occupy a space exactly equal to their original size, but usually a bit more. This is because the minimum recordable unit on a CD is the logical block. In ISO, just as in the DOS file system, directories are also files, and also take up space.

The Yellow Book (the standard defining the physical format of CD-ROM) specifies that the CD data starts after a pause of two seconds. This means that the first two seconds on a CD are not available for user data.

Information from: http://www.cd-info.com/CDIC/Technology/CD-R/Premastering/cdr_essentials.html