Generally, writable DVD discs come in 12cm (120 mm) and 8cm (80 mm) diameter sizes. The most commonly used is the larger 12cm type
A (12cm) "4.7 GB" media has 4.7 * 1 000 000 = 4.700.000.000 bytes / 1024/1024/1024 = 4.377 GB
4.7 GB disc stores 4.7 billion bytes [4:700,000,000 bytes ÷ 1000 = 4,700,000 KB ÷ 1000 = 4,700 MB ÷ 1000 = 4.7 GB]
Note: usable space may in fact be smaller ie around 4.27GB, due to sectors and disc formatting
Further:
Writable DVD discs can either be single (SS 4.7 GB) or double-sided (DS 9.4 GB) or double-sided double-layer ~17 GB (rare)
The amount of information that can be written is determined by the disc’s recording capacity as well as the physical and logical formats used.
All writable DVD formats devote the same amount of usable space to data (2,048 bytes per sector). DVD+R, DVD+RW and DVD-RAM specify the number of sectors available for user information (4.7 GB DVD+R/+RW 2,295,104 sectors, 4.7 GB DVD-RAM 2,295,072 sectors) so disc capacity can be calculated by multiplying the user data area size by the number of disc sectors. For example, a 4.7 GB DVD+R disc: 2,048 bytes/sector x 2,295,104 sectors = 4,700,372,992 bytes. This rounds to roughly 4.7 GB (decimal notation).
DVD-R and DVD-RW, on the other hand, do not stipulate the number of sectors that are dedicated to user information but simply that a minimum capacity must be available on the disc. In the case of DVD-R (version 1.0) this is 3.95 (12 cm) and 1.23 (8 cm) billion bytes and for DVD-R (Authoring), DVD-R (General) and DVD-RW 4.7 (12 cm) and 1.46 (8 cm) billion bytes. Consequently, real world capacity can vary slightly among discs from different media manufacturers although many have informally settled on 2,298,496 sectors (4,707,319,808 bytes) for a DVD-R (General) 4.7 GB disc.
Be aware, however, that the logical format (UDF, FAT, HFS etc.) as well as any defect management system employed consume space otherwise available for user information
Each DVD sector contains 2418 bytes of data, 2048 bytes of which are user data. And has in total 4,700,372,992 bytes on the entire disc
Therefore using maths (and approximating the amount of total usable data space on a DVD 4.7GB Disc)
4,700,372,992 ÷ 2048 = approximately 2,300,000 files (but more
likely around 1.5 Million due to loss of space\burning program used\type of format\ etc etc
This information mostly (but not all) has been taken from here:
http://www.osta.org/technology/dvdqa/dvdqa6.htm
And here:
http://en.wikipedia.org/wiki/DVD
And here:
http://www.google.com
Does that answer your small question?