Over the years, you may have wondered whether or not you have been duped when you bought a new computer with a hard drive of a higher capacity that your current computer or maybe when you just buy a new drive to put into your existing computer. The shop of manufacturer may advertising one capacity but Windows may report something different.
It can be a bit puzzling but there is an explanation.
Windows 7 - Disk Management
The above is a screenshot of the disk management console on my computer. I have two fixed drives in my computer, specifically:
- Disk 0
- 128GB SSD
- Windows reports 119.42GB
- Disk 1
- 1TB HDD
- Windows reports 931.51GB
So why is there a difference? Where did my 68GB go?
It comes down to simple mathematics. Originally, operating systems used “base 2” as the measurement unit for storage whilst disk capacities have always used “base 10”. In real terms, under “base 2” measurement, Windows allocated:
- 1024 bytes to 1 kilobyte,
- 1024 kilobytes to 1 megabyte,
- 1024 megabytes to 1 gigabyte,
- 1024 gigabytes to 1 terabyte
- etc.
This contrasts against “base 10” measurements of:
- 1000 bytes to 1 kilobyte,
- 1000 kilobytes to 1 megabyte,
- 1000 megabytes to 1 gigabyte,
- 1000 gigabytes to 1 terabyte,
- etc.
So under “base 2”, 1 terabyte is comprised of 1,099,511,627,776 bytes 1024^4 bytes) versus 1,000,000,000,000 bytes (10^12 bytes) under “base 10”. Seemingly, that is a difference of over 99GB of space on the scale of a 1TB “base 2” hard drive versus a 1TB “base 10” hard drive.
So how does Windows get 931.51GB from 1TB?
Quite simply, to convert 1TB from “base 10” to “base 2” in terms of bytes, we need to divide by 1,073,741,824 (1024^3 bytes, representing 1GB in bytes in “base 2”) which yields the result of 931GB.
So the good news is that you aren’t getting less than what you are paid for, just that Windows is stuck in old school mode reporting the capacity of your hard drive.
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