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I bought a new 32GB microSD card. Windows says the capacity is 29.3GB (31,474,057,216) in Properties for the drive. Why?

I expected 1024x1024x1024x32 = 34,359,738,368 bytes. I can accept 0.5GB for the file system, but not 2.7GB. There is no logical reason why the addressable space would follow base 10, since the addresses are in binary. (Or are they?)

Chloe
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2 Answers2

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If you check the fine print, you may find that 1M is defined as 1,000,000, not 1,048,576. And 1G is defined as 1,000,000,000, not 1,073,741,824

This has been a trick used by hard drive manufacturers for decades. And it appears that the memory card people have picked up the same trick from hanging out with their sleazy hard-drive marketing friends.

Richard Crowley
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The underlying media (flash memory) is measured in binary units, but flash cells become damaged over time. The "leftover" space is used to balance wear so that the media lasts longer than each individual cell.

Ignacio Vazquez-Abrams
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