Available memory of a 16GB microSD card?

Question

Out of my newly bought Class 10 16GB microSD card I am getting only 14.71GB. Is this normal?

Answer 1

Gigabytes are base 10, but Android uses Gibibytes (base 2)
See: http://www.wolframalpha.com/input/?i=16GB+to+GiB.
This is needed because binary data is written in base 2, but SI units are base 10.

Answer 2

Adding on to @GiantTree's answer, the binary-metric confusion is definitely one reason you encounter these kinds of differentially reported storage counts. Another thing is the formatting / file system overhead involved.

Normally, larger the SD card, larger will be the lost available storage due to the storage space required by the file system data structures like allocation tables, etc.

Android uses FAT32 or VFAT for SD cards by default, and, yes, this formatting does cause a significant loss in available storage.

Note also that newer Android devices or devices with modified kernels can support other file systems on the SD card such as ext4, NTFS or exFAT. All of these file systems have larger overheads compared to the FAT32/VFAT default, and ext4 and NTFS the highest among these.

As @Edgar posted, this can be thought of as the difference between the volume of a container measured internally and externally. The file system overheads account for the thickness, and the other part involves a different system of units used for measurement.

Put together, the decimal(metric)-binary confusion, file system overheads and also manufacturing issues cause this difference between advertised and reported storage capacity.

About manufacturing defects, I'm quoting from the accepted answer to this Unix&Linux SE question:

Typically a part of flash storage is faulty, and is marked so during manufacturing. There are also other bits that can go wrong (becoming unchangeable, unsettable, or unclearable), these parts must be marked faulty as well during the lifetime. This information is stored in a reserved space, on the same chips as your data. This is one of the several reasons a 4GB thumb drive is not showing 2^32 bytes capacity.

Answer 3

Also, all disks have 'bad sectors' which are not reported in the user available space.

Another thing that takes up space in a drive is the file structure inherent in the device itself.

A good way to understand this is to measure the exterior front wall of your house, then go from room to room, measuring the inside dimensions, omitting the interior walls and total up THOSE dimensions. Not the same, are they?