Option 2: Format USB to FAT32 with Terminal For example, Mac doesn't allow you to format 32 GB and smaller SD cards as MS-DOS (FAT32). The reason why MS-DOS (FAT32) is greyed out on your Mac could be that the option is unavailable for the USB drive you are formatting. MS-DOS FAT is Mac's name for the FAT file system, including FAT32, FAT16, so when MS-DOS (FAT32) is greyed out, you can just format a USB drive to FAT32 with the MS-DOS FAT option on Mac. What is the difference between MS-DOS FAT and MS-DOS (FAT32)? And why is the FAT32 option greyed out?
It is very confusing that sometimes you get both MS-DOS FAT and MS-DOS(FAT32) in Disk Utility and in some cases, the MS-DOS (FAT32) option is greyed out. You can remove it from the Mac computer and use it in Windows PC or your card. Now your USB drive has been formatted as MS-DOS (FAT32). Step 6: When the format process is complete, click Done. Step 5: Select Master Boot Record and click Erase. Step 4: In the Erase menu, enter a new name for your USB thumb drive if needed and select MS-DOS(FAT) or MS-DOS(FAT32) for format. Step 3: Select the connected USB drive and click Erase on the top. Step 2: Go to Applications > Utilities > Disk Utility. Step 1: Plug the flash drive that you want to format into your Mac computer. Normally, you can format a USB drive to FAT32 in Disk Utility on Mac. Option 1: Format USB to FAT32 in Disk Utility