1. Insert the SD card into your computer. Your computer should have a thin, wide slot on its housing; this is where the SD card goes.

-Insert the SD card into your computer. Your computer should have a thin, wide slot on its housing; this is where the SD card goes.
-Many newer Macs don't have an SD card slot, so you'll need to purchase an SD-to-USB adapter in order to connect your SD card.

2. Open the Finder. It's a blue, face-shaped icon in the Dock.

3. Click Go. This menu item is on the left side of your Mac's menu bar, which is at the top of the screen.

4. Click Utilities. It's in the Go drop-down menu.

5. Double-click Disk Utility. It's in the middle of the Utilities page.

-The utilities on this page are usually arranged alphabetically.

6. Click your SD card's name. You'll see it in the window that's on the far-left side of the Disk Utility page.

7. Click the Erase tab. It's at the top of the Disk Utility window.

8. Click the box below the "Format" heading. This box is in the middle of the page. Doing so causes a drop-down menu to appear with the following format options:

-Mac OS Extended (Journaled) - The default Mac format. Only works on Mac.
-Mac OS Extended (Journaled, Encrypted) - Encrypted version of the default Mac format.
-Mac OS Extended (Case-sensitive, Journaled) - Version of the default Mac format that treats files with the same name differently if there are case differences (e.g., "file.txt" and "File.txt").
-Mac OS Extended (Case-sensitive, Journaled, Encrypted) - A combination of the three above formatting options for the Mac format.
-MS-DOS (FAT) - Works on both Windows and Mac computers, but has file size limit of 4 gigabytes.
-ExFAT (Recommended) - Works on both Windows and Mac computers. Has no storage limit.

9. Click a format you want to use. Doing this will set your selected format as the preference for your SD card.

10. Click Erase, then click Erase when prompted. Doing so will cause your Mac to begin erasing and reformatting your SD card. Once this process is complete, your SD card will support your selected format.

and you're finished