Why Windows 7 recognize a 4GB SDHC card only with 3.68 GB? How to format/get 4GB?

Question

I have a Kingston SDHC card 4GB class4, but on Windows 7 it's recognized only with 3.68 GB space available;

I've already formatted the card and I get only 3.68GB; How I can get 4GB space available on the card?

thanks

max

Answer 1

The reason for the discrepancy is that Kingston is labeling the card based on the base-10 value of GB, where one GB is 1000000 bytes, while Windows is reporting the card based on the base-2 value of GB (also called GiB), where one GB is 1073741824 bytes.

4 * 1000000000 / 1073741824 is equal to roughly 3.7.

The answer is that you can't get 4 GB of space available because your card physically doesn't have that much space.

You can see http://en.wikipedia.org/wiki/Gigabyte for more information.

Hard drive and storage manufacturers like to use 10^9 as the value for a GB because it lets them advertise more space. 2^30 is the actual relevant measurement.

Answer 2

This is common. The size of the card is advertised as 4GB where 1GB is 1,000 MB. However, that is not accurate. There are actually 1,024 MB in a full GB. Manufacturers use the "1,000" all the way through the conversion instead of the correct 1,024.

Using the proper number to calculate gigabytes should give you something like 4GB = 4,194,304 bytes. However, the manufacturer advertises 4GB = 4,000,000. 4,000,000 bytes is, in fact, around 3.68GB.

Answer 3

Binary/Decimal differences is one option, but I think in the case the "missing" space is simply reserved during formatting for file system information... it's why you can have a file with a really long name that's still shown as taking up zero space on the drive. Those file names and other metadata have to be stored somewhere.