Sep 04, 2014

Why does actual HDD capacity always differ from what is listed on the packaging and label?

Why is there always a discrepancy between the stated size of a HDD and the size I see when I go into My Computer on Windows and check the size there? Windows always show slightly less actual capacity that the manufacturer’s’ stated capacity. Are the manufacturers just rounding up to make them sound bigger, sort of the reverse of stores always pricing things as $X.99 to make it seem like you aren’t spending as much?

Seagate has a good page about this:


" Hard drive manufacturers market drives in terms of decimal (base 10) capacity. In decimal notation, one megabyte (MB) is equal to 1,000,000 bytes, one gigabyte (GB) is equal to 1,000,000,000 bytes, and one terabyte (TB) is equal to 1,000,000,000,000 bytes.

Programs such as FDISK, system BIOS, Windows, and MacOS use the binary (base 2) numbering system. In the binary numbering system, one megabyte is equal to 1,048,576 bytes, one gigabyte is equal to 1,073,741,824 bytes, and one terabyte is equal to 1,099,511,627,776 bytes.

Simply put, decimal and binary translates to the same amount of storage capacity. Let's say you wanted to measure the distance from point A to point B. The distance from A to B is 1 kilometer or .621 miles. It is the same distance, but it is reported differently due to the measurement."
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