Storage Capacity of Recordable DVD or DVD-R

by Alan D
(New Zealand)

A single layer DVD-R with 4.7GB capacity and a dual layer DVD+R disc or DVD+R DL with 8.5GB capacity.

The indication on a DVD5 disk is that it will hold 4.7GB of data. How much of that space is readily accessible for data that I want to write to the disk? For example, if I write 4.7GB of data to a DVD5 disk, will all my data be readable and retriable? 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 recording a movie on a DVD5 disk, it will not go over about 4.3GB. This leaves an area of 400MB not written too. Is it possible the software I am using is causing this problem?

First, 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 movie discs or software discs. There is a DVD5 disc, 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 layers (readable from the same side) with a capacity of 8.5GB. The two data layer DVD-Rs are the 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