Storage Capacity of Recordable DVD or DVD-R

by Alan D
(New Zealand)

A DVD5 disk says that it will hold 4.7GB of data. How much of that space is useable for data that I want to write to the disk and be readily accessed? For example, if I write 4.7GB of data to a DVD5 disk, will all of my data be able to be read and retrieved? There must be room for a Table of Contents (TOC) and other things that the disk may have to have there.

I have noted that when I have placed a movie on a DVD5 disk that it will not go over about 4.3GB. This leaves an area of 400MB not written too. Is it possibly the software that I am using that is causing this problem?

First of all, DVD5 is normally a term used for replicated DVD discs or read-only DVD discs. In other words, discs that you buy commercially with the information already on it. You cannot record to these discs. Examples are the movie discs or software discs. Basically, you have DVD5 which is a single layer disc, DVD10 is a double sided disc with a single data layer on each side of the disc (disc flipping is required), DVD9 is a two data layer disc readable from the same side (no disc flipping required), and finally DVD18 which has two data layers on each side of the disc.

Your question is about DVD-R discs which are recordable DVDs. DVD-Rs or DVD+Rs can be single data layer with a stated capacity of 4.7GB or two data layer (readable from the same side) with a capacity of 8.5GB. The two data layer DVD-Rs are identified as DVD-R DL or DVD+R DL. Note that the dual layer disc is not double the single layer capacity due to some capacity loss in order to make the dual data layer technology work.

Now to answer your question, the problem rests in the use of terminology when it comes to DVDs. All DVD-Rs that are single data layer state a capacity of 4.7GB. Unfortunately, GB does not refer to gigabytes like for the size of files, but rather to billions of bytes or G bytes. The G in this case refers to SI units (K = kilo or 1000, M = mega or 1,000,000, G = Giga or 1,000,000,000). When talking about computer storage it is not SI units that are used but rather binary units. Binary units use multiples of 2 rather than 10. So in binary units (1 KB = 1 kilobytes or 1024 bytes, 1 MB = megabyte or 1048576 bytes, 1GB = gigabyte or 1073741824).

Therefore, stated capacity of a single layer DVD-R is 4.7 GB but in this case it means 4,700,000,000 bytes which converted to computer GB gives 4.37. The calculation is 4,700,000,000 divided by 1,073,741,824. The file capacity is 4.37 GB and if your files are larger than this, they will not fit on a single layer DVD-R.

It basically has nothing to do with the type of disc used, recorder, or software for burning. Using two different burners, two different computers, and two different types of burning software, here are my results:

  • Computer 1 – 4.36 GB or 4,690,923,922 bytes used and 15 MB free according to burning software

  • Computer 2 – 4.36 GB or 4,690,923,922 bytes used and 15 MB free according to burning software

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