Kilo Bytes Per Second vs. Kilo Bits Per Second (KBps vs. kbps)


Well this post tries to clarify the confusion that many have regarding KBps and kbps (I was one too). If you read through this post it will make a lot of things clear.

Measure of file size: KBps
File size i.e. how big the file or how much space a file occupies in the hard disk measured in terms of KiloBytes (KB upper case “K” and upper case “B”). In computing terms the upper case “K” stands for 1024. 1024 is computed from 210. (2 power 10). 2 denote the number of characters in the binary system which is used to store data in the disc (ones and zeroes).
Other abbreviations like mega, giga and terra also use the base as 1024,

1KB (KiloByte) = 1024 Bytes (approximately 1000 Bytes)
1MB (MegaByte) = 1024 KB (approximately 1000 KiloBytes or 1 million Bytes)
1GB (GigaByte) = 1024 MB (approximately 1000 MegaBytes or 1 billion Bytes)
1TB (TerraByte) = 1024 GB (approximately 1000 GigaBytes or 1 trillion Bytes)

Measure of data transfer speeds: kbps
Data transfer speed over the networks (including the internet) is calculated in terms of bits per second: kilobits (kb small case “k” and small case “b”). The higher the kbps i.e. more the bits transferred per second, more the speed, faster the network/connection. Here k stands for 1000 (103 )

1 kbps (kilo bits per second) = 1000 bits per second
1 Mbps (mega bits per second) = 1000 kilo bits per second.
1 Gbps (giga bits per second) = 1,000 mega bits per second.

ISP bandwidth and download speeds
The most common confusion caused by the similarity of KBps and kbps is when it comes to internet bandwidth and download speeds. People often complain that their ISP promised 512kbps connectivity but they are seldom able to download any file at 512 KBps. They fail to notice the difference in cases of the units and hence think their ISP is cheating them or offering them poor quality service. As mentioned earlier data transfer speeds are always calculated in terms of kilo bits per second (kbps) so an ISP connectivity of 512 kbps promises of transfer of at the max 512 kilo bits per second.

On the other hand, file size measure is always in Kilo Bytes and thus download speeds are always calculated based on how many Bytes per second are downloaded and hence Kilo Bytes per second (KBps). KBps and kbps are not interchangeable.

So an internet connectivity of say 512kbps can never achieve a download speed of 512 KBps. To calculate the maximum download speed of a “X kbps” connection, we need to use a simple formula as below.

Download KBPS speed = (Kbps value*1000) /8)) / 1024.

I.e. For a connectivity of 512 kbps

kbps value * 1000 = 512 * 1000 = 512000

512000 / 8 = 64000

64000 / 1024 = 62.5 KBps

Therefore theoretically an internet connection of 512kbps bandwidth can download at a speed of 62.5 KBps

If you don’t want to go through all the hassles of the above formula, just multiply the kbps value with 0.1220703125 to get the KBps value.

512 kbps * 0.1220703125 = 62.5 KBps. Simple!

Internet connectivity Download speed (approx)
256 kbps 31.3 KBps
384 kbps 46.9 KBps
512 kbps 62.5 KBps
768 kbps 93.8 KBps
1 mbps ~ 1000kbps 122.1 KBps

I have mentioned download speed as approximate because they will vary (always reduce) by 15 – 20% due to network signal loss, computer hardware overheads etc. So for realistic, real world figures always reduce 15 – 20% from the computed KBPS download speeds
Now I guess the confusion of kbps and KBps has cleared away. Just remember when you talk in terms of network it’s always bites per second (bps) and when you talk in terms of storage and files its always Bytes per second (Bps). And next time you won’t complain when your 512 kbps connection does not give you download speeds of 512KBps because now you know why 🙂


  • this article is really valuable for those,who really wants to charge themselves with the latest technology

  • Your article is very helpful. Lately I have been experiencing quite low download speeds and was convinced that Optus Cable Broadband was not as fast as claimed in advertisements, 8 Mb/sec. Maybe I am wrong. has a speed program which on several tests showed my speed to be in the order of about 587 kb/sec.


  • The problem is the ISP’s sell their service without mentioning the difference. Especially now that they sell 1.5 megabyte and 6 megabyte speeds and you cannot get near those speeds. Usually they will say something to the effect that it’s the server on the other end that’s slow. If that were the case, then the download would be at the same slow ass speed whether you had a 1.5 meg or a 6 meg connection.

  • This document is really very good. I always get confused between Kbps and KBps now its very good.

    Thanks for posting such a awesome document.

  • upper case KBps)means kilo bytes per second which is for storage eg. memory cards. small case kbps) means kilo bits per seconds which is the speed of a connection per second eg. broadband speed of upto 8 mbps (mbps stands for mega bits per second) so it does make sense.

  • Thank You !
    I’m stuck on dial up and this really helps a lot. I’ll stop bitchin’ at the phone company now and lookin’ stupid.
    Got to get that satellite installed ! No other options.
    Thanx again !

  • Thank You Very Much !
    Now I won’t sound like an idiot when I bi**h at ATT or my ISP.
    Got to get that dish installed !
    No other options.
    Thanx again !

  • I thought.. i knew every thing about computer before this.. thanks for the information

  • I think the internet providers really take advantage of this confusion, when saying they offer 2MBs, so it’s not just us, it’s them being unfair.

  • Yes, they did not mention the difference between KBps and kbps. So we’re confused why our internet connection is so slow then. Thank you so much for your info.

  • I had some idiot salesman from Telstra try and convince me to transfer from my current provider to Telstra by trying to tell me that Telstra provide 1500 Kbps as opposed to my other provider supplying 1500 kbps. Well he was wrong and I told him to go home. Luckily I knew what I was talking about however for those who don’t know any better he may have conned them. Shame on you Telstra, Shame on you Telstra sales guy! The tech info provided here is great! Well done.

  • Well, who do you talk to when you call your ISP? Tech support? Customer Service? Trust me, they wouldn’t know the difference. ISP’s skilled engineers never answer the phone and never talk to end user so don’t blame on ISPs.
    Very good article. I’ve been in computer business for several years and I’v always got confused.
    Keep up the good work 🙂

  • Thanks a lot for brief explanation…
    Finally i come to know this by you…
    It will realy helpfull to all….:)

  • Dude… nice explanation… but the shortest way to explain this could have been:

    1 Byte = 8 bits… 🙂

    Anyways, good goin’!!

  • Excellent, lucid explanation, except that the formula 1 Byte = 8 bits
    figures nowhere in the article.
    All that us lowly non-nerds can do is wonder why, in these days of simple, straightforward decimals, that the original development nerds found it necessary to complicate matters by specifying that 1 Byte had 8 bits and not exactly 10, and 1 Kilo Byte = 1024 Bytes and not 1000 exact Bytes!!
    Crazy!… or is there a valid, reasonable explanation??

  • Thank you for this article.
    This article elaborates more than required information to differentiate between kbps and KBps. So will be very useful which are not techi ones.

  • Are you really sure about 8 bits to the byte?

    In transmission technology each byte (character) always has associated start and stop markers.

    The start marker is of 1 bit duration.
    The stop marker is, most commonly, 1 bit duration as well ( but certainly used to be 1 1/2 or 2 bits long) and, occasionally there was yet an additional bit for parity.

    I mostly reckon 10 bits = 1 Byte.

    Do transmission packets dispense with the start/stop bits and use CRCs or the like for error detection/correction? If so how are these overheads taken care of in the bits / byte computation?

  • Thanks for solving a decade old mystery for me. I guess all of us b****ing at our ISP have learnt our lesson: Read the fine print and pay attention to the case of the letter!!!

  • The providers aren’t being unfair, they can not guarantee you an exact download speed as there are many factors which determine this. They can however guarantee what ADSL service will be programmed to your phone line.
    For example, ADSL2+ is ‘up to 24MB’. NOBODY actually gets 24MB, unless you live inside your phone exchange. People will complain because they thought they signed up for a guaranteed 24MB service. It may seem like false advertising but you should really read and research the technology and what you’re signing contracts for instead of blaming the ISP.
    Great page btw, I use it all the time to explain this to people.

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