Before we tell you how many photos we have found fit on different capacities, it's important to note that it is necessary for a flash drive to allocate a small amount of space for its own firmware to make it operate.
It is standard for 5-10% of a drive's capacity to be reserved as unusable space. It is also standard industry practice to state a flash drive's capacity based on physical memory, not available memory.
Now that we have that out of the way, below are general capacities for 4, 8, 16, 32 and 64GB flash drives:
Have additional questions about which capacity is right for you? Contact our Customer Care Team at firstname.lastname@example.org so that we may better assist you!