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The difference in capacities is due to two different methods for defining what exactly the prefixes mega, giga, tera mean. In the computer world, these prefixes have different meanings depending on what exactly you are talking about. Hard drive manufacturers report the size of hard drives using the decimal definition of these terms (10^6, 10^9, 10^12 resepctively), whereas operating systems and other software use the binary definition of these terms (2^20, 2^30, 2^40).

As you can calculate, these values are close, but not exactly the same. 10^6 is 1,000,000, but 2^20 is 1,048,576. Once we get to larger hard drive sizes, the difference really becomes noticeable.

One gigabyte in binary is 1,073,741,824 bytes (2^30), but in decimal it’s only 1,000,000,000 bytes (10^9), which is a difference of 73,741,824 bytes (~70MB). So, when we're talking about storage size in gigabytes a hard drive's capacity as reported by the OS will be about 7% less than what is advertised by the hard drive manufacturer.

40GB = 37GiB
80GB = 74GiB
100GB = 93GiB
120GB = 111GiB
160GB = 148GiB
200GB = 186GiB
250GB = 232GiB
300GB = 279GiB
320GB = 297GiB
400GB = 372GiB
500GB = 465GiB
750GB = 697GiB
1000GB = 930GiB

Since consumers don't think in base 2 mathematics, manufacturers decided to rate most drive capacities based on the standard base 10 numbers we are all familiar with. Therefore, one Megabyte equals one million bytes while one Gigabyte equals one billion bytes. This isn't too much of a problem with fairly small numbers such as a Kilobyte, but each level of increase in the prefix also increased the total discrepancy of the actual space compared to the advertised space.

Here is a quick reference to show the amount that the actual values differ compared to the advertised for each common referenced value:

* Megabyte Difference = 48,576 Bytes
* Gigabyte Difference = 73,741,824 Bytes
* Terabyte Difference = 99,511,627,776 Bytes

Based on this, for each Gigabyte that a drive manufacturer claims, they are over reporting the amount of disk space by 73,741,824 Bytes or roughly 70.3 MB of disk space. So, if a manufacturer advertises an 80 GB (80 billion bytes) hard drive, the actual disk space is around 74.5 GB of space, roughly 7% less than what they advertise.

emmibe skrifaði:Svoleis, þá fer ég nú bara í búðina og fæ 140 GB endurgreidd

emmibe skrifaði:Svoleis, þá fer ég nú bara í búðina og fæ 140 GB endurgreidd

emmibe skrifaði:Haha, þetta hefði nú þótt slatti af geymslumagni fyrir x árum. Keyptu þér úlpu og það vantar aðra ermina.

zdndz skrifaði:bara pæling, má þá auglýsia þennan disk sem 1,5 TB

When referring to hard drive capacity, one gigabyte, or GB, equals one billion bytes. Your computer's operating system may use a different standard of measurement and report a lower capacity.

nonesenze skrifaði:í windows allavega er 1mb = 1024kb, 2mb = 2048kb

hvartaðu frekar í microsoft hahahahaha

emmibe skrifaði:Svoleis, þá fer ég nú bara í búðina og fæ 140 GB endurgreidd

JReykdal skrifaði:Eru makkarnir ekki búnir að breyta þessu hjá sér?

Farnir að nota KiB/MiB/GiB fyrir base2 tölur og KB/MB/GB fyrir base10 eins og SI segir til um?

emmibe skrifaði:Var að versla harðann disk sem er 1,5 TB en er bara 1,36 TB bara að spá hvað 140 GB eru notuð í þar sem þetta er flakkari?????