At What Point does an ISO Become too Large for a DVD ???

I have searched and researched this and am getting a lot of conflicting information.

All of the various blank DVDs that I have say 4.7-GB.

Often, when burning picture files, I have went within a few mb of the 4.7-GB capacity with no negative issues that I was able to detect.

However, I have read in several places that an ISO must be kept below 4-GB, else it will either refuse to burn, or any files beyond 4-GB will be corrupted; some state 3.8-GB to be the maximum; then, others say that, so long as they are less than 4.7-GB, they will burn and work fine.

I have created a custom ISO that is 4.02-GB; common sense tells me that I should be fine on a standard 4.7-GB DVD; will I or not ?

I trimmed some unnecessary info to get it down to 4.02-GB; would I have been okay to have left it at closer to 4.6-GB ?

Thanks for reading and all help is appreciated.

Hi BuckSkin had you read the Wikipedia article?
The citation states that ISO 9660 Format defines file length to be a 32 bit value.
I make that 4,294,967,295 bytes of contigious data.
So, although the blank DVD has a capacity of 4.7 GB, ISO 9660 is only defined to be 4.2 GB.
Would that be consistent with your own research?

iko22 said:

Hi BuckSkin had you read the Wikipedia article?
The citation states that ISO 9660 Format defines file length to be a 32 bit value.
I make that 4,294,967,295 bytes of contigious data.
So, although the blank DVD has a capacity of 4.7 GB, ISO 9660 is only defined to be 4.2 GB.
Would that be consistent with your own research?

Thank you so much !

For some curious reason or other, wikipedia never came up in my searching.
You have better answered my confusion in a few words than in all of the reading I have done thus far, and in words that make sense to me.
So, if I am understanding, my 4.02 GB should be safely under the 4.2 GB and I should be alright, ----- right?

Thanks again!

Yes it is apparent that a files size of 4.02 GB safely conforms with the image file standard .

ISO or data is irrelevant, it's down to decimal and binary - 1000 vs 1024. Manufacturers quote the size of DVDs, HDDs in decimal because it looks better value for money. DVDs are actually 4.37GB.



I wish I had a quid for every post I've seen that moans 'I bought a 4TB HDD and it only holds 3.63' etc. I think Mac uses decimal for storage size.

The IEC, IEEE, EU, and ISO standard definitions matter, otherwise we shall all just be confusing one and another.


Prefix- decimal definition
kilo- 1000 = (10^3)
mega- 1000000 = (10^3)^2
Giga- 1000000000 = (10^3)^3
Tera- (10^3)^4
Prefix- base 2 definition
kilo- 1024 = (2^10)
mega- 1048576 = (2^10)^2
Giga- 1073741824 = (2^10)^3
Tera- (2^10)^4


To illustrate:
1 Gigahertz is a decimal unit and equals a unit of 10^9 hertz, whereas 1 Gigabyte is a binary unit and equals a unit of 2^30 bytes.

townsbg said:

If you get a double layered DVD then you will have twice the room. However not all drives are compatible with double layered disks especially the older ones.

How does one determine whether a DVD drive is capable of double-layer or not ?

Ranger4 said:

This website should answer most of the questions on DVD R DL that you wish to know.

Thank you !