iStorage/Kanguru defines a gigabyte (GB) as 1,000,000,000 bytes. The storage capacities may vary depending on the operating system. The actual capacity reported by systems like Windows is often lower.
In Windows operating systems, an xx GB [e.g., 16 GB] flash drive has a minimum reported capacity of xx GB [e.g., 14.4 GB]. Product storage capacity is also used for device formatting and internal functions.