Why do 16GB phones only have 12GB storage available?

What exactly is phone storage?

For Android phones, the storage includes RAM (Random Access Memory) and storage (some people call it ROM). RAM is the active running memory of your phone, and is used to store temporary data and exchange cache data with the CPU. Storage, on the other hand, is considered to be the storage capacity for your phone – it's the equivalent of the computer hard drive which is used to store data.

For Apple iPhone, the capacity shown in the setting refers to the actual storage capacity, although it will not display the RAM available on your iPhone. According to official Apple data, the RAM of iPhone models before the iPhone 6 / 6 Plus is 1GB RAM while iPhones onward all have 2GB RAM.

Why do 16GB phones only have 12GB storage available?

1. The operating system consumes space

Just like a desktop-based OS such as Windows PC, the primary drive (e.g. the "C" drive) has some space used even if you haven't stored anything – the same principle applies to your phone too. The operating system obviously occupies some space on your device, different operating systems and versions consumes different space. The following picture shows the OPPO X9007 with the Android 4.4.4 operating system consuming a massive 4GB on the Android phone.

2. Binary and decimal calculations lead to different storage

Generally speaking, the memory card manufactures adopt decimal calculation when producing storage devices. According to this method, 1GB=1000MB, however MS Windows OS uses a binary calculation, which means 1GB=1024MB. Meanwhile, Android and iOS system both adopt binary calculation when recognizing the storage space, so the different calculation methods lead to a perceived decrease in storage capacity. The following examples clearly show the specific conversions between binary and decimal calculations.

Note: the left digits (8GB, 16GB, 32GB, and 64GB) are the storage capacities using binary calculation, also known as nominal storage, while the digits on the right (7.45GB, 14.9GB, 29.8GB, and 59.6GB) represent the actual storage available under decimal calculation, known as actual storage.

3. Storage medium NAND Flash blocks occupy part space

Storage medium is physical medium for the data storage, e.g. CD, DVD, hard disk, USB flash disk, SD card and so on. Both NAND Flash and eMMC are the two main forms of storage media for various mobile devices; eMMC is the updated version of NAND Flash, and up to 99% mobile phone storage solutions utilize NAND Flash.

However there is a significant problem. Due to its inherent structure and workmanship, NAND Flash cannot always ensure memory block integrity, leading to bad blocks being randomly generated and occupying the storage of NAND Flash. This is therefore another possible cause for your lost storage. For a more technical explanation, please refer to the figure below:

For the above reasons, it becomes apparent why 16GB phones have just 12GB of storage available to them: the OS, different calculation methods, and bad blocks occupying NAND Flash are the three main reasons. While it's not physically possible to address these factors, you can still resolve them.

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