I have a kingston usb data traveler flash disk 512 mb size. I have not formatted it , all I do is just install it in the usb port and it is recognised automatically. When I rt click on it the size of the disk is reported as 491 mb. Is this size ok ? Is it normal ?

Sorry I mistyped. I am losing 21 mb and not 12 mb of space.

not sure if this is the answer, but it is usually the answer on hard discs that show a lower capacity than on the label. a kilobyte is 1024 bytes. a megabyte is 1024 kilobytes (1048576 bytes). But some makers class a kb as 1000 bytes and a mb as 1000kb. This makes the number of mb they advertise a higher number than it really is. so if they do it that way then 512mb divided by 1.048576 = 488 'real ' megabytes.

In other words the flash drive manufacturer uses the decimal capacity (512MB) that translate to approx 460mb in binary capacity as read by the OS. It has been that way ever since they invented HD. Read the fine print on the product description. i_XpUser

In short, that is normal.