QUOTE (tsantee @ Jan 13 2006, 05:49 AM)

The real capacity of an 8.5 GB DL disc is 7.95 GB. The reason for the difference is that computers add bytes differently than do marketing departments.
Here's a more detailed explanation:
As modern computers use base-2 to represent all data and instructions, originally (and quite logically) powers of two were used to measure quantities of bytes, thus 1 MB == 2^20 or 1,048,576 bytes. Disk drive manufacturers then decided to play a little game with capacity figures using powers of 10, thus 1 MB == 10^6 or 1,000,000, thus slighltly but usefully inflating disk capacities.
In 1998 practice was enshrined in IEC standards (now endoresed by the IEEE and CIPM) and the original power of two based units were renamed: thus the original megabyte is now properly referred to as a mebibyte and the original gigabyte is now referred to as a gibibyte.
[See:
http://en.wikipedia.org/wiki/Mebibyte and
http://en.wikipedia.org/wiki/Base2]
The situation is further complicated.
Disk formatting tools continue to measure capacity using power of two measurements (i.e. mebibytes and gibibytes) but report them using the prefixes now ascribed by the IEC to power of ten measurements (i.e. megabytes and gigabytes). Similarly, memory capacity continues to be measured using powers of two but again, capacities are stated using the prefixes ascribed by the IEC to power of ten measurements.
So, as per the IEC, DVD-R capacities are truthfully stated and most tools that work with DVD media properly translate powers of ten measurements into powers of two measurements. However, users who are doing their own bit budgeting and/or who are otherwise unaware of the sitation are easily caught off guard and surprised!
Michael Lazar