Tyler Durden's Fight Club Blog

HDD's - the Advertized size vs the Actual size. - Windows 7 Help Forums

If you wonder why your 500 Gbyte disk only reports 465 Gbyte in your system, read on.

   Information

A drive that is advertised as a 500 Gbyte actually contains 500.000.000.000 bytes

The manufacturers just divides it three times by 1000 to show the value in Gbytes, but that's not accurate.

   Information

1 Gbyte = 1024 Mbyte,
1 Mbyte = 1024 Kbyte
1 Kbyte = 1024 byte

To calculate the actual size we need to divide it three times by 1024.

   Information

500.000.000.000 byte / 1024 = 488.281.250 Kbyte

. . 488.281.250 Kbyte / 1024 = . . . 476.837 Mbyte

. . . . .476.837 Mbyte / 1024 = . . . . . . 465 Gbyte

The actual size of the disk is not 500 Gb, but 465 Gb
With a 1TB disk it's the same thing, because 1 Tbyte = 1024 Gbyte
A 1Tb disk is actually only 1000.000.000.000 byte, which equals 0,9 Tb (931 Gb)
You actually get 69 Gb less than you thought you paid for.

An alternative method to calculate the real size is to use ratios: thanks to Airbot

   Information

For Gbyte the ratio is 0.9313226

500 Gbyte multiplied by 0.9313226 = 465.6613 Gbyte

   Information

For Tbyte the ratio is 0.9094947

2 Tbyte multiplied by 0.9094947 = 1.8189894 Tbyte or 1,819 Gbyte