This discussion is as much to do with the smaller .IMG file size limit of 2,147,483,647 Bytes [2GiB minus 1 Byte] required by some older Garmin units and GMXT, and then it's moot if you can simply put the <2GiB image on a 4GB card as is pointed out in the above posts for only those units capable of reading FAT32. The confusion over the decimal Gigibyte [GB] and the binary Gibibyte [GiB] is never-ending and can unfortunately be further perpetuated by use of non-standard abbreviations such as 'gig' [not a criticism, i do it too at times but avoid it in sensitive situations such as these discussion].

When Windows reports in 'GB' as in the pics above, it's actually sticking with the original binary convention of 2 to the power of 30 i.e. 1,073,741,824 bytes for a Gigabyte, which is historically correct but is now not the interpretation thrust upon us some time back by the sneaky drive manufacturers who decided to measure storage space in decimal i.e. 1,000,000,000 for a Gigabyte which is 10 to the power of 9. Of course, that all started back in the '90s when were were measuring flash drives and SD cards only in Megabytes [1MB is 1,048,576 bytes in binary base of 2^20 and of course it's 1,000,000 bytes in decimal base of 10^6 so the difference is relatively small, >5%], but now when we measure hard drives in Terabytes and 1TiB is 1,099,511,627,776 and in decimal TB it's only 1,000,000,000,000 bytes we're looking at ~10%. Soon we'll be measuring our home PC HDD in Petabytes [or Pebibytes if you like] and the difference between binary and decimal is then profound. Don't even try to think about Exabytes.

How did this get handled by the the International Electrotechnical Commission (IEC)? Over 15 years ago in December 1998 they decided to 'standardize' the terminology by making KB/MB/GB/TB etc decimal and KiB/MiB/GiB/TiB etc binary. Unfortunately Microsoft didn't see it that way so confusion has reigned ever since because to M$ when you talk computers everything is binary.....

Let's just try to use the 'correct' abbreviations: GB for Gigabyte, GiB for Gibibyte and not use GB when we mean GiB like M$ does, and resist any usage such as 'gig' please.