From the title, this sounds a whole lot like a repeat of this question, but it isn't, I promise. Because he wanted to know whether you could tell from looking at a cable whether it was Cat-5 or Cat-5e, based on a few pictures and some really shoddy termination.

My question is a lot more theoretical.

What, if any, is the actual, real, honest-to-God, difference between Cat-5 and Cat-5e? I've read the wikipedia entry, and while informative, it could really do with a rewrite. One of the few sections that mentions Cat-5e is The Cat 5e 350mhz debacle. The title makes me believe that maybe the 350mhz denotation is how you can tell, but then it goes and says this:

"Although the performance of this new 350 MHz cable was slightly better it was an easy way to sell the consumer on future proofing their needs while charging around 15% more and leading to a higher margin on the 350 MHz cable than the standard 5e cable.

Well, alright then, what IS a standard 5e cable?

I looked at some more resources, and found some sadly incorrect suggestions and no real answers. For instance, this wiki answers post says that you need Cat-5e to get Gb/s speeds, that 5e is rated at 350mhz, and that there's less crosstalk (though it doesn't say why). Of course, it also says "Unless every single component in the network is gigabit rated, then you will never have a gigabit network, because your network will always run at the speed of your slowest device.", so you can understand my skepticism.

The second table on this page sounds pretty solid, basically displaying that there are standards for Cat5E that don't exist for Cat5, with the assumption that the cable meeting those standards will perform better/faster than a cable without those particular requirements.

But of course, I wanted to ask, because you can't trust everything you read on the internet. Case in point? connectworld.net, who either desperately need to update their page, or desperately need to stop taking drugs:

"The Simple Answer: CAT-5 is rated to 100M CAT-5e is rated to 350M CAT-6 and CAT6e is rated to 550M or 1000M depending on your source CAT-7 is supposedly rated to 700M or presumably 1000M

Today there is no approved CAT-6 or CAT-7. While some folks are selling products they call Level 6 or 7, there aren't even specs for them, making CAT-5e the best available option.

Sad, really. I blame the schools.

So now I ask you. I assume that there is an actual, real difference between Cat-5 and Cat-5e. what is it?


Hrm. The plot thickens.

It appears that Cat-5 cable is defined by the TIA/EIA-568-A standard. The only time I've ever paid attention to that standard was when crimping my own ends, because TIA/EIA-568-A specifies the order of the wires in the RJ45 (really 8P8C) end. It also uses the green pair first, which I thought was weird, since I learned orange first.

However, when I go to the TIA/EIA-568-A wiki page, I'm redirected to the TIA/EIA-568-B page. At a table way down at the bottom are the lines:

Cat 5: Currently unrecognized by TIA/EIA. Defined up to 100 MHz, and was frequently used on 100 Mbit/s Ethernet networks. May be unsuitable for 1000BASE-T gigabit ethernet.

Cat 5e: Currently defined in TIA/EIA-568-B. Defined up to 100 MHz, and is frequently used for both 100 Mbit/s and 1000BASE-T Gigabit Ethernet networks.


I still don't know what the actual difference is, aside from orange going first in Cat-5e, apparently, but hey, more light on the subject, I guess.

Edit 2

It appears that Able Cables hired someone to research and write a paper on the difference between TIA/EIA-568A and TIA/EIA-568B. Here is his conclusion:

9.0 Conclusion

Historically 568B was the specification on choice due to its early development and implemented base, but as the market and the political climate has changed over the years 568A has become the more dominate and preferred specification. This is only due to a desire by world standards organizations to provide a specification as backwardly compatible as possible. All new installations should be carried out using the 568A standard and cables only to be terminated to 568B specification on existing 568B systems.

I'm not entirely sure what to think of that.

  • Interesting question. A quick search for the specs turns up nothing of value and of course Wikipedia should never be used as a technical reference. Jan 28, 2010 at 13:46
  • 1
    dude, get some work done :) (or watch some Tim and Eric reruns at least) - I'm a huge Devil's fan by the way, anywhere nearby?
    – Chopper3
    Jan 28, 2010 at 14:38
  • +1. for the Tim & Eric reference. Tom goes the Mayor. ;)
    – joeqwerty
    Jan 28, 2010 at 14:48
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    If you really want to find out, you'll need to buy the Standards documentation, but it's fairly expensive. techstreet.com/standards/TIA_EIA/568_SET_CD?product_id=1525793
    – joeqwerty
    Jan 28, 2010 at 14:55
  • I would explain to you what the difference is (NEXT, ELFEXT, return loss) but since you guys protected this question you're gonna have to live with your server fault (and amusingly amateurish accepted answer). So google those terms and thou shall be enlightened. Or at least look at something like ieee802.org/3/tutorial/nov02/tutorial_2_1102.pdf for some measurements. Dec 2, 2015 at 17:59

5 Answers 5


I believe that the difference between 5 and 5e is a more specific description of the twists per pair and twists per foot of each pair.

Cat5a and Cat6 further enforce the geometry of the pairs relative to each-other over the course of the entire cable and restrict the untwisted amount at the ends.

In practice, if it says Cat5, it is an old cable. "Cat5" hasn't been made in years, and any twisted pair cable suitable for use in networking (ie not cat3 or something used for a thermostat or lawn sprinklers) will be a Cat5e or better.

A true Cat5 installation is sufficient for gigabit ethernet. I've seen plenty of things labeled cat5 that are not actually up to spec for one reason or another, that run 100mb fine but don't work with gig.


You got part of it right. I won’t go into the exact standards for each, but in general:

Cat 5 is rated to 100 MHz, but was specified when only 10BASE-T and 100BASE-TX Ethernet was common. Both of those only transmit on one pair in each direction.

Cat 5e is also rated to 100 MHz, but includes specifications for testing parameters important to 1000BASE-T (Gigabit Ethernet). Gig Ethernet transmits four pairs simultaneously in parallel. If a signal leaks from one pair to another it disrupts the other pair. Thus, the new specification with extra required tests at the “far end.” [Note: 1000BASE-TX is not an Ethernet standard - more marketing and such.]

Cat 5E (capital letter) is a marketing spin produced by cable manufactures to tempt you into buying their brand instead of the cheaper alternatives. Does not apply to networking standards.

Cat 6 – hmm. Around 1998 the cable manufacturers needed something new so they proposed 200 MHz to the standards bodies. The standards bodies asked for 250 MHz instead, estimating the requirement for 10 Gig Ethernet. It is rated to 250 MHz, but no standard pushed this.

Cat 6e or Cat 6E – another marketing spin trying to capture market share before the next standard came out. They anticipated the “e”, so when the standard finally came out the standards bodies couldn’t use that letter designation.

Cat 6a – is rated to 500 MHz. When the 10GBASE-T (10 Gigabit Ethernet) standard finally came out they had additional test requirements beyond what Cat 6 was specified to deliver, so this standard was published.

Cat 7 – only exists in cabling components (cable and connectors), but not an assembled link. The closest to a next-higher cabling standard is the ISO Class F. No existing Ethernet standard requires it.

You also mentioned T568A and T568B. Electrically they are identical. However, when that was specified there were some … political differences … between various big companies on the standards committee. One camp had been using the first color code, the other camp had been using the second. The compromise was to have two color codes in the standard. As long as you only use one color code around your building you should be fine. If you mix them then you get crossed pairs.

These and lots of other exotic network trivia are found in a recently published book: Network Maintenance and Troubleshooting Guide, 2nd Edition. http://www.amazon.com/Network-Maintenance-Troubleshooting-Guide-Solutions/dp/0321647416/ref=ntt_at_ep_dpi_1

  • Is there a good way to check and see if I have mixed pair in the walls? The cables I purchase all seem to be A but I believe that the wiring in the wall is A, I'm lazy and don't want to check every outlet if possible.
    – Drewdin
    Feb 3, 2015 at 14:12

Neal's answer is essentially the same answer I reached after researching various multiple sources. However, to make things simple when I talk to others about cables, I sum it up as follows:

Cat5 - 4 Twisted Pair, shielded or unshielded, rated at a carrier frequency of 100 MHz, rated to support 100 Mbps, but may support 1000 Mbps.

Cat5e - 4 Twisted Pair (pairs have varied twists to reduce various interferences), shielded or unshielded, rated at a carrier frequency of 100 MHz, rated to support 100 Mbps and 1000 Mbps.

Cat6 - 4 Twisted Pair (pairs have varied twists to reduce various interferences, along with separation or shielding between pairs), shielded or unshielded, rated at a carrier frequency of 200 MHz, rated to support 100 Mbps and 1000 Mbps, but may support higher.

Cat6a (a as in augmented) - 4 Twisted Pair (pairs have varied twists to reduce various interferences, along with separation or shielding between pairs), shielded or unshielded, rated at a carrier frequency of 500 MHz, rated to support 100 Mbps and 1000 Mbps, but may support higher.

Carrier frequency does not equal throughput, but can be thought of as the cable's immunity toward localized or environmental interference. The higher the carrier frequency, theoretically, the less susceptible the cable should be to EMI, RFI, and various crosstalk. Theoretically because improper wire runs or bends can reduce the cable design's immunity; especially with UTP (Unshielded Twisted Pair) cabling.

Simply put, choose the category cable based upon the desired or potential speed of the network, and then choose the one with the higher carrier frequency. While some stores might sell a Cat5e 100 MHz cable, you can also find Cat5e 350 MHz cable of the same length at other stores for the same price or less. If you choose to err, then err on the side of caution by choosing the higher carrier frequency... in the hopes that it actually will better protect against noise and crosstalk.


First TIA/EIA-568-B is the second version of the specification, it replaced teh 568-A version. There were several addenda in between. T568A and T568B (whcih color pair is pair 1) are specified in the standard document EIA/TIA-568-A.

The categories are defined in the standard ONLY by the specific tests cables have to pass. There is nothing in the spec about what coppy alloy to use or how many twists per foot. Vendors can use any geometry they want AS LONG AS IT PASSES THE TESTS.

When cat 3 was the most common cable most vendors met the standard for cat 5 for reduced crosstalk at a higher frequency than the tests for cat 3 by increasing the pitch (twists per inch) and using a different pitch for each pair. That was PART of the difference but visible to guys that crimped or punched down cable so that became folk lore as the only difference.

Most cat6 and higher cables use a cruciform plastic spacer to keep the four pairs apart and reduce crosstalk.

Cat5e is tested up to 100Mhz, cat6 to 250Mhz and cat6A to 500Mhz. The soon to be ratified EIA/TIA-568-C revision includes cat7 and cat7a which is tested at 1Ghz.

http://www.siemon.com/us/white_papers/07-03-01-demystifying.asp is a good guide to the differences.


Basically higher-spec cabling has a better quality of copper and insulation, thus maintaining adequate crosstalk limits at higher frequencies.

  • 2
    The downvote isn't from me, but I believe the OP was looking for something a lot more precise that included details about physical and functional differences.
    – Zoredache
    Jan 28, 2010 at 17:27
  • It wasn't from me either. but you get a +1 (Underrated) ;-) Jan 28, 2010 at 17:50
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    It was from me. I'm sorry but this answer feels like Chopper3 didn't read the question. The asker goes to great lengths to emphasize that he doesn't want to know if it's better -- it's more expensive so it's better be -- he wants to know what, exactly, is the difference, in the specs. "Better quality of copper" is about as helpful as "duh, it's got electrolytes."
    – niXar
    Jan 28, 2010 at 18:03
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    haha , nice Idiocracy ref :) - Matt and I have been around here for quite a while and my answer was kind of a joke for his benefit to be honest, it's factually correct however but certainly lacking detail so I fully understand so don't sweat it, I've stopped collecting points anyway :)
    – Chopper3
    Jan 28, 2010 at 18:40
  • 1
    Yep, Chopper is just in it for the women and the cars, now Jan 28, 2010 at 19:46

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