Some of the flash storage device's listed capacity is used for formatting and other functions and thus is not available for data storage. 

When a flash storage device is manufactured, steps are taken to ensure the device operates reliably and permits the host device (e.g., computer, digital camera, PDA, etc.) to access the memory cells for data storage and retrieval. These steps, referred to as "formatting" uses some of the memory cells, reducing the capacity available for data storage.  



To increase performance and endurance, some SSD manufacturers will reserve some of the drive capacity from the user area and dedicate it to the controller. This practice is known as over-provisioning (OP) and will increase the performance and longevity of the SSD. All current Kingston SSDs feature over-provisioning, and the capacities are 120GB, 240GB, 480GB, 960GB, 1.92TB and 3.84TB. Learn more about over-provisioning.