Today I would like to demystify the kilobyte issue and explain why there are sometimes large differences between an advertised devices’ capacity, and the capacity that same device displays in Windows and other operating systems. I will also explain the difference between kilobyte, kilobit and kibibyte.
If you just want to convert a kilobyte to another value (megabyte, megabit, gigabyte, gigabit etc) then use the Byte Converter further below, but if you want to learn about bits and bytes and their multiples, then read on!
Contents
 Kilobytes, Megabytes, Gigabytes
 Download conversion charts (PDF)
 Bit, Byte, Kilobyte Converter
 Conclusion
Kilobytes, megabytes, gigabytes
First, let’s get some things out of the way. Bits, bytes and their multiples is a very confusing issue, and I have tried very hard to lay everything out in an aseasytounderstand way however, don’t expect this to be in any way easy, it’s hard (at first anyway). It certainly doesn’t help when manufacturers use the wrong terms to describe their product capacity (not kidding). I would describe the whole situation as a dog’s breakfast, but hey, that’s just my opinion 🙂
Now let’s get straight into the different definitions of a kilobyte, which varies according to the standard being used.
Kilobyte (Binary, JEDEC)
A Binary kilobyte is a digital information unit that is a multiple of a byte, specifically: 1 kilobyte (KB) == 1024 bytes (B). In the Metric system, kilo means 1000, so using the term "kilo" in this context has caused much confusion. It gets even more confusing when hardware manufacturers of storage (hard drives/optical discs/optical drives/flash storage, with the exception of RAM) and data communications (networking and other data rates) actually use a different methods to calculate the storage capacity or speed of thier products (they use Decimal kilobytes and kilobits, more on this later).
Kilobyte (Binary, JEDEC) profile 


Term  Abbreviation  Bytes  Standard  
kilobyte  KB (uppercase K and B, asper JEDEC)  1024  Binary, JEDEC  
Used for measuring…  


1 kilobyte (KB) == 1024 Bytes (B) 


Kilobyte (Decimal, Metric)
Next we have to the Decimal kilobyte which is made up of 1000 bytes, specifically: 1 kilobyte (kB) == 1000 bytes (B) and is used for data storage (hard drives, flash drives and optical discs etc) and sometimes data communication rates (networking). This is the reason why you can buy a USB flash drive that is advertised as having a 64GB (gigabyte) storage capacity, but shows up in Windows and other operating systems as having only 59.6GB. This is because the manufacturer measures data capacity in 1000 byte blocks (Decimal), however your Windows or other operating system measures the same device using 1024 byte blocks (Binary) hence the smaller size.
Kilobyte (Decimal, Metric) profile 


Term  Abbreviation  Bytes  Standard  
kilobyte  kB (lowercase k, uppercase B)  1000  Decimal, Metric  
Used for measuring…  


1 kilobyte (kB) == 1000 Bytes (B) 


Kibibyte (Binary, IEC)
Now in order to clear up the confusion between a Binary (1024 byte) and a Decimal (1000 byte) kilobyte, the IEC enacted standards with new names for all Binary prefixes for 1024bytekilobytes, which replaces the term kilobyte with kibibyte, megabyte with mebibyte, gigabyte with gibibyte, and so on (see table below). These changes are in the hope that we will all refer to a Decimal kilobyte (1000 bytes) as a kilobyte, and the Binary kilobyte (1024 bytes) as a kibibyte. This is in unison with the Metric System where the term "kilo" means 1000.
Kibibyte (Binary, IEC) profile 


Term  Abbreviation  Bytes  Standard  
kibibyte  KiB (uppercase K, lower case i, uppercase B)  1024  Binary, IEC  
Used for measuring…  


1 kibibyte (KiB) == 1024 Bytes (B) 


Kilobit (Decimal, Metric)
Next we have the Decimal kilobit which consists of 1000 bits of digital information and is most often used to express data communication rates, as in networking. For example: an ADSL line speed can be expressed as 1500kbps, which means the connections’ capacity is 1500 kilobitspersecond. The same ADSL connection can also be expressed as being 1.5Mbps which means 1.5 megabitspersecond. Please note that a kilobit is in no way comparable to a kilobyte and it’s best not to confuse the two. A kilobyte actually consists of 8192 bits whereas a kilobit (Metric) has 1000 bits.
Kilobit (Decimal, Metric) profile 


Term  Abbreviation  Bits  Standard  
kilobit  kbit (lowercase k suffixed with lowercase "bit", subsequent values have an uppercase first letter ie. Mbit)  1000  Decimal, Metric  
Used for measuring…  


1 kilobit (kb) == 1000 bits (b) 


Kilobit / kibibit (Binary, JEDEC / IEC)
Finally we have the Binary kilobit (JEDEC) or kibibit (IEC) which consists of 1024 bits of digital information and is most often used to express CPU cache and RAM memory capacities. As with the 1000bitkilobyte vs 1024bytekilobyte issue, the IEC enacted new names for Binary kilobits and renamed them kibibits, mebibits, gibibits etc in the hope we will now refer to a kilobit as consisting 1000 bits, and a kibibit as consisting of 1024 bits. Please also note that some chip/memory manufacturers stll use the Metric prefixes when referring to Binary multiples, further confusing consumers.
Kilobit / kibibit (Binary, JEDEC, IEC) profile 


Term  Abbreviation  Bits  Standard  
kilobit kibibit 
Kbit (uppercase K suffixed with lowercase "bit") Kibit (uppercase K suffixed with "ibit") 
1024  Binary, JEDECand IEC  
Used for measuring…  


1 kilobit (Kbit) == 1024 bits (b)1 kibibit (Kibit) == 1024 bits (b) 


Bit, byte, kilobyte conversion charts (PDF)
You might want to download and print these charts for your reference etc.
Bit, byte, kilobyte quick reference chart PDF 
Bit, byte conversion chart PDF 
Byte Converter
Enter the value you want to convert in the appropriate field, for example: If you wanted to convert 1 binary megabyte into decimal kilobytes, enter 1 into the megabyte/mebibytes field in the middle column (3rd down), click the Calculate button, and the result will be in the right column, 2nd down (1048.576kB).
Conclusion
It can take a few lightbulb moments in order to fully grasp the whole kilobyte issue, but if you’re still stuck then read over this article again or perhaps visit some of the links below for further information. If after doing all that you’re still stuck, just email me and I’ll help you out.
Cheers!
Wikipedia links
 Bit at Wikipedia
 Byte at Wikipedia
 Kilobyte at Wikipedia
 Kilobit at Wikipedia
 Metric at Wikipedia
 IEC at Wikipedia
 JEDEC at Wikipedia
Fumigator says
I think it would be helpful to explain how you get 1024 bytes out of 1 kibibyte. Did you think it would confuse people more to explain that in binary, multiples are calculated differently than in decimal, i.e. 1 KiB = 1 byte * 2 * 2 * 2 * 2 * 2 * 2 * 2 * 2 * 2 * 2? You can’t just assume 1 KiB = 1 byte * 10, because that’s a decimal calculation. In my opinion this is the root of the confusion– people try to perform decimal calculations instead of binary ones. For example, someone I know recently was confused why if 500 KiB = 512000 bytes, why then didn’t 1 MiB (500 KiB * 2) didn’t equal 1024000 bytes (512000 bytes * 2)? Well, it’s because he was making the assumption 500 KiB is half of 1 MiB, which it isn’t. In reality, half of 1 MiB is 512 KiB, not 500, and he saw that once we worked through the binary calculations.
Richie Brereton says
Hi Fumigator, yep great point and thanks for your comment. I will edit the doc soon to show the different calculations as I think too it will help people understand it better. cheers! Richie