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A kilobyte is actually 1000 bytes. "kilo-" is an SI prefix meaning "1000".

  • 1 km = 1000 meters
  • 1 kg = 1000 grams
  • 1 kB = 1000 bytes

When dealing with computer memory, the addresses for each memory location are typically binary numbers, which means the total number of addresses is a power of 2. It makes the most sense to use all of these positions, so the total capacity of a memory will typically be a power of two.

Since 210 is equal to 1,024, it is often approximated as "1 kilobyte" in speech, but this is just a shorthand, not a real definition.

RAM manufacturers treat this as a literal meaning instead of an approximation, though, and extend this to higher powers, which conflicts with the way units are used elsewhere. So a "1 GB" RAM IC has 230 = 1,073,741,824 bytes instead of 1,000,000,000 bytes, a 7% error. On the other hand, a 1 GB Flash memory actually doeshave around 1,000,000,000 bytes, as you would expect.

"kB" or "KB" can mean either 1024 bytes or 1000 bytes, depending on who you ask. Both meanings have been in use since the early days of computing, confusing users ever since.

kilo- means 1000, and has for centuries, so where did 1024 come from? The answer is binary addressing.

Your basic transistor, the foundation for all things computer, has 2 states (on/off), which is known as binary. So modern computers of all types use the binary numbering system (0/1 = off/on).

Memory addresses in computers are a number of bits wide. For instance, the old 6502 microprocessor had memory addresses 16 bits 'wide'.

With 10 bits, for instance, a computer can address 210 memory locations, which is 1024. With 16 bits, a computer can address 216 memory locations. So the number of memory locations is always a power of two. It wouldn't make much sense to make memory chips that don't use all of the addressable locations, so all memory is in powers of two. (This doesn't apply to other computer components, however. Hard drives, disk drives, DVDs, and other media, clock speeds and data rates and networking speeds are all measured in powers of 10.)

But 1024 is 210 (2 to the 10th power), conveniently close to 103 (1000). In computers, base-2 shows up over and over again. It's easier to approximate and say "1k" instead of 1024. 1 kilo is normally 1000, as per the metric system's prefixes.

In this case, the next higher size of memory chips was often 2x or 4x the previous size. This pulled folks away from the normal base-10 thinking toward base-2 thinking ... and we ended up with something that sounds like it is based on powers of 10, but is really based on powers of 2.

Officially, 1000 is the only valid meaning, and "k" was used by engineers for 1024 just as an approximation. (2048 bytes isequal to 2.0 kB, after all.) Over time, this approximation became used by marketing types as if it was actually defined as1024, rather than just being used as an approximation.

In 1968, for instance, Donald Morrison talked about how it was confusing to tell laymen that doubling a 32K memory produced a 65K memory. He proposed to end the confusion by using the Greek letter κ (kappa) to mean 1024, but this never stuck. Instead, people started using capital K to mean 1024, which further increased confusion instead of helping.

Nowadays however, there is a new prefix to be used for the non-standard meaning:

  • 1 kibibyte (KiB) is 1024 bytes
  • 1 kilobyte (kB) is 1000 bytes

So too for the old megabyte which was 220 bytes:

  • 1 mebibyte (MiB) is 1,048,576 bytes
  • 1 megabyte (MB) is 1,000,000 bytes.

Higher units like terabyte have always been used with the 1000x meaning except in rare cases.

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โˆ™ 2012-09-07 14:34:11
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Q: Why is 1 KB commonly said to be 1024 bytes instead of 1000 bytes?
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Related questions

What is 1024 bytes commonly known as?

1024 bytes is a kibibyte (KiB).1000 bytes is a kilobyte (kB).

Why 1024 bytes rounded to 1000 bytes?

1024 bytes is binary counting while 1000 bites is decimal counting.

1000 bytes equals?

1024 bytes = 1KB, or kilobyte 1024 KB = 1MB, or megabyte

How many bytes in 640 MB?

640 x 1024 x 1024 bytes (data transfer) 640 x 1000 x 1000 bytes (storage)

What is the biggest byte?

The official prefixes only go as high as 1024 or 280 bytes.1000 MultiplesBit = 1 Binary DigitByte = 8 BitKilobyte = 103 bytes = 1000 bytesMegabyte = 106 bytes = 1000 kilobytesGigabyte = 109 bytes = 1000 megabytesTerabyte = 1012 bytesPetabyte = 1015 bytesExabyte = 1018 bytesZettabyte = 1021 bytesYottabyte = 1024 bytes1024 MultiplesFor sequential numbers based on 1024 (210) instead of 1000 :Bit = 1 Binary DigitByte = 8 BitKibibyte (kilo-binary-bytes) = 210 byte = 1024 bytesMegabyte = 220 bytes = 1024 kibibytesGibibyte = 230 bytes = 1024 mebibytesTebibyte = 240 bytesPebibyte = 250 bytesExbibyte = 260 bytesZebibyte = 270 bytesYobibyte = 280 bytes

Which is smaller a kilobyte or a byte?

Kilo means 1000. A kilobyte is 1000 bytes...or more accurately, because bytes are counted in the binary system, that would be 1024 bytes (210=1024).

How many bytes are in a gigabyte -?

In general, the prefixes and their corresponding quantities are kilo = 1000 Mega = 1,000,000 = 1000 x 1000 Giga = 1,000,000,000 = 1000x 1000 x 1000 In computer terminology, however, rather that being powers of 10, the prefixes are mapped to powers of 2 which come closest to those powers of 10 1 kilobyte = 1024 bytes ≈ 1000 1 Megabyte = 1024 x 1024 = 1024 kilobytes = 1,048,576 bytes ≈ 1,000,000 1 Gigabytes = 1024 x 1024 x 1024 = 1024 Megabytes = 1,073,741,824 bytes ≈ 1,000,000,000

How many bytes are in 3.5 GB?

well there are 1000 bytes in a kilobyte. 1000 kilobytes in a megabyte. and 1000 megabytes in a kilobyte. therefore i would say 3500000000 bytes = 3.5 GB actually, there are 1024 bytes in a kilobyte 1024 kilobytes in a megabyte and 1024 megabytes in a gigabyte therefore 3.5 GB is exactly 3,758,096,384 bytes

Why is 1 kB 1024 bytes instead of 1000 bytes?

1024 is the closest number to 1000 you can reach in the binary system of counting. Hard drive manufacturers use decimal counting to rate there drives which is why you don't get exactly 100GB out of a 100GB hard drive.

1000 bytes equals 1 megabytes?

1 megabyte = 1048576 bytes. 1000 bytes is almost 1 killobyte (1024 bytes is exactly 1 killobyte).

What unit of memory stores 1024 kilobytes?

1 kilobyte (KB) = 1000 bytes 1 kibibyte (KiB) = 1024 bytes 1024 KiB = 1 mebibyte (MiB)

What is equal to exactly 1024 bytes but often is rounded down to 1000 bytes?

kB (kilobytes) is usually taken to mean 1024 bytes, even though the prefix "kilo" has a different meaning (exactly 1000) in physics.

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