# Why do CD's only hold 74 minutes? **URL:** \ **Category:** Factual Questions\ **Created:** [June 2, 2000, 10:30pm UTC](https://boards.straightdope.com/t/why-do-cds-only-hold-74-minutes/21246 "2000-06-02T22:30:32Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![Saxman](https://avatars.discourse-cdn.com/v4/letter/s/f6c823/32.png) [@Saxman](https://boards.straightdope.com/u/Saxman)\ **Post date:** [June 2, 2000, 10:30pm UTC](https://boards.straightdope.com/t/why-do-cds-only-hold-74-minutes/21246/1 "2000-06-02T22:30:32Z")
Hey all, longtime reader, first-time yada yada. Even got into an argument with a high school history teacher way back when, because she insisted that Frank L. Baum DID write the Wizard of Oz as a populist metaphor. When I showed her Cecil’s column nixing her take ([http://www.straightdope.com/classics/a1\_392.html](http://www.straightdope.com/classics/a1_392.html)), she just told me not to believe everything I read. So, I started harassing her about every lecture handout she gave the rest of the year. Anyway, my question: I’ve seen some recordable CD’s that can hold 700 megabytes, as opposed to the standard 650 MB/74 minutes capacity. I mentioned my shock to a friend, and he told me that the 650 MB standard is purely arbitrary. Seventy-four minutes (and however many exact seconds), he continued, is the precise length of Beethoven’s Fifth Symphony, which was chosen as the industry standard. What gives? I’m bothered to think that the music industry so whimsically decided to limit how much music I can illegally copy onto a single CD. ---
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [June 2, 2000, 11:20pm UTC](https://boards.straightdope.com/t/why-do-cds-only-hold-74-minutes/21246/2 "2000-06-02T23:20:44Z")
Check the archives and you’ll see this question has been answered about 650 million times. ---
**Author:** ![Saxman](https://avatars.discourse-cdn.com/v4/letter/s/f6c823/32.png) [@Saxman](https://boards.straightdope.com/u/Saxman)\ **Post date:** [June 2, 2000, 11:34pm UTC](https://boards.straightdope.com/t/why-do-cds-only-hold-74-minutes/21246/3 "2000-06-02T23:34:45Z")
Figured it was an obvious question, but alas, after repeatedly futile archive search attempts (with keywords “CD”, “length”, “74”, etc.), I grew weary of sifting through the myriad tangential threads that turned up, like “Who Loves Mammaries?”…8^) ---
**Author:** ![Arnold\_Winkelried](https://avatars.discourse-cdn.com/v4/letter/a/3d9bf3/32.png) [@Arnold\_Winkelried](https://boards.straightdope.com/u/Arnold_Winkelried)\ **Post date:** [June 2, 2000, 11:38pm UTC](https://boards.straightdope.com/t/why-do-cds-only-hold-74-minutes/21246/4 "2000-06-02T23:38:49Z")
The 74-minute length being related to the length of Beethoven’s 9th symphony may or may not be an urban legend. See snopes: [Roll Over, Beethoven](http://www.snopes.com/music/media/cdlength.) However, that maximum limit is not the physical maximum, but a standard adhered to for compatibility with most players. I have several compact discs at home that have 80 minutes of music. Here’s what the [Winn L. Rosch Hardware Bible, Premier Edition](http://viking.delmar.edu/courses/Cis312J/EBOOK/wrh12.htm#E67E12) has to say: > [@](#): > > The nominal maximum capacity of a CD amounts to 74 minutes of music recording time or about 650MB when used for storing data. These capacities are only approximate, however. A number of factors control the total capacity of a given disc. For example, mass produced audio CDs sometimes contain more than 74 minutes of sound because disc makers can cram more onto each disc by squeezing the track on the glass master disc into a tighter, longer spiral. This techniques can extend the playing time of a disc to 80 minutes or more. > The special CDs that you can write on with your PC cannot benefit from this tighter track strategy because their spiral is put in place when the discs are manufactured. The standard formats yield four capacity levels on two different sizes of disc, as discussed in the CD-R section below. In any case, these numbers represent the maximum storage capacity of a recordable CD. Nearly anything you do when making a CD cuts into that capacity. ---
**Author:** ![C\_K\_Dexter\_Haven](https://avatars.discourse-cdn.com/v4/letter/c/b2d939/32.png) [@C\_K\_Dexter\_Haven](https://boards.straightdope.com/u/C_K_Dexter_Haven)\ **Post date:** [June 3, 2000, 12:19pm UTC](https://boards.straightdope.com/t/why-do-cds-only-hold-74-minutes/21246/5 "2000-06-03T12:19:42Z")
As a new DVD owner, I’m astounded. The DVD disk – same size as a CD disk, now – can hold a two hour movie, that’s sound and picture!.. plus information on cast and credits, plus a “Making of” featurette, plus several foreign language versions. So the CD disk can clearly hold a helluva lot more music than 80 or 90 minutes. ---
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [June 3, 2000, 1:27pm UTC](https://boards.straightdope.com/t/why-do-cds-only-hold-74-minutes/21246/6 "2000-06-03T13:27:59Z")
The DVD and the CD standards are quite different. The CD standard was developed for 2 channel, 16 bit, 44Khz sampling, no compression. Since this standard was adopted we’ve come a long way but the CD-audio standard remains unchanged, probably for compatibility reasons. A DVD is something else. ---
**Author:** ![DVous\_Means](https://avatars.discourse-cdn.com/v4/letter/d/9fc29f/32.png) [@DVous\_Means](https://boards.straightdope.com/u/DVous_Means)\ **Post date:** [June 3, 2000, 2:58pm UTC](https://boards.straightdope.com/t/why-do-cds-only-hold-74-minutes/21246/7 "2000-06-03T14:58:22Z")
DVD’s achieve their remarkable capacity to some very clever compression algorithms developed by the MPEG group. There is also a neat technique of storing sata at diffent physical levels within the silicon/metal mix, which can be resolved by using a laser that resolves at differing wave and focal lengths. In this manner, DVD’s can potentially hold up to 17 gigabytes. ---
**Author:** ![handy](https://avatars.discourse-cdn.com/v4/letter/h/b5a626/32.png) [@handy](https://boards.straightdope.com/u/handy)\ **Post date:** [June 3, 2000, 3:45pm UTC](https://boards.straightdope.com/t/why-do-cds-only-hold-74-minutes/21246/8 "2000-06-03T15:45:35Z")
Yep. My 2x cd writer takes about 30 minutes to test & write a full cd. I wonder how long it would take to write something that is 32 times as large? PLus, dvds use both sides to get that much data on. ---
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [June 3, 2000, 4:59pm UTC](https://boards.straightdope.com/t/why-do-cds-only-hold-74-minutes/21246/9 "2000-06-03T16:59:59Z")
“only” 74 minutes? You gotta be kidding. When they developed that standard getting that much information on a disk was a huge feat! And if you understood what is involved you would appreciate it. Only later was the CD appropriated for computer data since it was so well suited. ---
**Author:** ![HorseloverFat](https://avatars.discourse-cdn.com/v4/letter/h/8e8cbc/32.png) [@HorseloverFat](https://boards.straightdope.com/u/HorseloverFat)\ **Post date:** [June 3, 2000, 5:44pm UTC](https://boards.straightdope.com/t/why-do-cds-only-hold-74-minutes/21246/10 "2000-06-03T17:44:19Z")
I think a unformated CD has the potential space for 700 megs of data, but its useless unless formated. There are many CD-Recorders that can read to the 80 minute mark, but once you start recording things past the standard stop point you’ll have a fine time finding compatible drives that can read that far. Most CD-ROMs won’t, and few if any CD-players will. Not exactly worth the extra six minutes.