Insert the SD card into your Mac’s SD card slot or a USB card reader
Open Disk Utility
Select the SD card from the sidebar
Click Erase
Choose a format:
ExFAT for use with Mac and Windows
MS-DOS (FAT) for compatibility with many devices
Mac OS Extended if it will be used only with older Macs
Choose a name for the card
Click Erase to format the SD card
Wait for the process to finish
Click Done when complete
Eject the SD card safely from Finder or Disk Utility