9 Replies Latest reply: Oct 31, 2011 7:33 AM by JohnTruth
JohnTruth Level 1 (10 points)

Sorry for such a simple question, but this is really bugging me.


At work I have CDs, DVDs and BluRay discs that are all branded with company logos etc.. so they look the same. Most of the time when I burn a disc I do it in Finder, but it doesn't say the capacity of the disc anywhere. 'Get info' doesn't help and Disk Utility doesn't shed any light either.


I know I should be more organised and label my discs, and I know I should probably use some other software but:


• I like burning discs in Finder; it's all I need (well not quite, evidently...)

• Surely there should be something to tell me if a disc is 700mb/4gb/8gb/25gb The only hint I get is an error message when I try to put too much data on a disc, but I'm not willing to burn every disc using trail and error...

  • Dashford Level 1 (15 points)

    Disk utility should tell you this info. Are you able to select the disk in the left pane? What do you see at the bottom right? It should provide CAPACITY, AVAILABLE, USED, NUMBER OF FILES. Are these showing as blank?

  • Radiation Mac Level 5 (4,645 points)

    Here are some capacities for you:


    You can look at the surface of the blank disk for the designation of which type of disk it is (CD-R,  DVD+R, etc.)


    DVD capacity
    Disk TypeData sectors
    (2,048 B each)
    DVD-R (SL)2,298,4964,707,319,8084.7
    DVD+R (SL)2,295,1044,700,372,9924.7
    DVD-R DL4,171,7128,543,666,1768.5
    DVD+R DL4,173,8248,547,991,5528.5
    SL / DL – Single/Dual layer


    CD-R, CD-RW Capacities: 700 MB


    How much data can you fit on a Blu-ray disc?

    A single-layer disc can hold 25GB.
    A dual-layer disc can hold 50GB.



    I pulled these off Google for you.


    Hope this helps


    Message was edited by: Radiation Mac

  • JohnTruth Level 1 (10 points)

    Thanks for the help guys.


    Radiation Mac: Thanks for the info, but I already knew the capabilities of the different discs - the problem was that the discs themselves have nothing on the top of them but my company logo, so no indication of whether they're CDs, DVDs or BluRays (useful I know...)


    Dashford: Thanks for this! I can select the Superdrive in the left pane, but it didn't give me any info in the bottom right. I had to go into 'Open System Information' and it had the disc type there under 'Media'.

  • JohnTruth Level 1 (10 points)

    Then again, it would be a lot more useful if I could see what Dashford is seeing: capacity, available, used, number of files etc.. Why can I not see these in my disk utility?

  • Dashford Level 1 (15 points)

    For example, I am currently in the middle of erasing an old Seagate external hard drive ...




    See at bottom right there are the capacity etc but you have to have the drive or partition selected on the left.

  • jsd2 Level 5 (6,200 points)



    I played with this a little in my Snow Leopard system, using both a blank CD-R disc, and also a CD-R disk that I had burned as a data CD using Finder.


    I think what is happening is that when a burned CD is placed in the optical drive, it has already been formatted such that the system recognizes it as a "volume" and mounts it onto the file system the same way that it would mount a regular disk partition. Finder and Disk Utility can read the information on this mounted volume and report its capacity, free space, etc, the same way that an external disk drive would be reported. Although the icon of a burned CD appears on the Desktop, this icon does not represent a physical object in your Home/Desktop folder, but rather represents a mounted object  with its "mount point" in the hidden /Volumes folder.  If you Get Info on it with Finder, it will be of kind:Volume:

    Screen shot1  2011-10-31 at 8.20.49 AM.png


    Screen shot2  2011-10-31 at 8.01.13 AM.png


    By contrast, when you insert an unburned, blank CD, it has not yet been formatted and cannot be mounted in the file system. You can see an icon on the Desktop that looks like a CD volume:

    Screen shot3  2011-10-31 at 8.12.07 AM.png


    However if you show all file extensions, you can see that the icon carries the extension ".fpbf" and is actually a "burn folder," not a mounted volume:

    Screen shot4  2011-10-31 at 8.12.41 AM.png


    Screen shot5  2011-10-31 at 8.08.16 AM.png


    Such a "burn folder"  is a real folder that gets created in Home/Desktop. Like any "folder", it does not have a "capacity":


    So basically, Finder and Disk Utility can give volume information for burned optical media that has been formatted and mounted, but not for blank media.

  • Kurt Lang Level 8 (36,645 points)

    If you have it, Toast gives you the information you're looking for. I put a blank CD, DVD and single layer Blu-ray disk in my drives. Press Command+I from within Toast and it gives you this type of information:







  • jsd2 Level 5 (6,200 points)

    If you don't have Toast, I just looked at the free (and nice!) utility Simply Burns, and its "data burn" window also shows the type and capacity of inserted blank media.

    Screen Shot 2011-10-31 at 10.02.32 AM.png


    Screen Shot 2011-10-31 at 10.03.40 AM.png

  • JohnTruth Level 1 (10 points)

    Thanks for clearing that up jsd2! Makes sense that it doesn't show that kinda info on blank media. Would be nice to see in the future though.

    I'll be using Simply Burns from now on.