# Hard drive capacity under Windows.
**URL:** https://boards.straightdope.com/t/hard-drive-capacity-under-windows/57670
**Category:** Factual Questions
**Created:** [March 12, 2001, 5:15pm UTC](https://boards.straightdope.com/t/hard-drive-capacity-under-windows/57670 "2001-03-12T17:15:42Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@Stupendous\_man](https://boards.straightdope.com/u/Stupendous_man)
#### Post date: [March 12, 2001, 5:15pm UTC](https://boards.straightdope.com/t/hard-drive-capacity-under-windows/57670/1 "2001-03-12T17:15:42Z")
My buddy bought what he thought was a 20 Gb hard drive. After formatting it, it reports a total capacity of 18 Gb. Does Windows 98 do anything that might account for the lost space, or is there some rounding-off procedure that harddrive manufacturers employ? What he wants to know is, all of the factors that might reduce the capacity by 2 Gb, but not show up.
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### Author:  [@Kestral](https://boards.straightdope.com/u/Kestral)
#### Post date: [March 12, 2001, 5:26pm UTC](https://boards.straightdope.com/t/hard-drive-capacity-under-windows/57670/2 "2001-03-12T17:26:27Z")
Hard drive specs are written by marketing people who sort of zoned out when the fact that computer “kilo”, “mega” and “giga” prefixes relate to powers of two, not powers of ten, was explained to them.
A real gigabyte is two to the power of 30, or 1,073,741,824, bytes. A hard disk marketing gigabyte is ten to the power of nine, a nice round 1,000,000,000, bytes. So a “15.3 gigabyte” hard drive is actually only 14.25 gigabytes, and that’s before you format it and lose a few per cent more of your space.
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### Author:  [@Arjuna34](https://boards.straightdope.com/u/Arjuna34)
#### Post date: [March 12, 2001, 5:36pm UTC](https://boards.straightdope.com/t/hard-drive-capacity-under-windows/57670/3 "2001-03-12T17:36:15Z")
To elaborate on **Kestral** ’s answer, the 20,000,000,000 byte hard drive is actually 18.6265 GB, since since 1 GB = 1,073,741,824 bytes.
Computer memory is sold with the power-of-2 quantities, so if you put a gigabyte of RAM in your machine, you’d have 1,073,741,824 bytes, not 1,000,000,000.
Arjuna34
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### Author:  [@Kestral](https://boards.straightdope.com/u/Kestral)
#### Post date: [March 12, 2001, 6:18pm UTC](https://boards.straightdope.com/t/hard-drive-capacity-under-windows/57670/4 "2001-03-12T18:18:55Z")
Thanks, Arjuna. I used 15.3 gig as an example because that was the only one I had figured out and knew the numbers for. 🙂