Partitioning an SD card helps protect and secure certain sensitive data on the card and also allows you to create a backup of programs and operating systems. Partition can also improve the performance of your computer or device. You can partition SD cards from Windows or Mac computer or from Android device.
Steps
Method 1 of 3: Partition SD card on Windows computer

Step 1. Insert the SD card or card adapter into your computer's USB port

Step 2. Select Start then Control Panel
You will access the window Control panel.

Step 3. Select the System and Security option, then Administrative Tools

Step 4. Next, select Computer Management
The computer management application will start and display on the screen.

Step 5. Select Disk Management on the left, under the Storage option

Step 6. Right click on the name of the SD card and choose New Simple Volume

Step 7. Click Next on the New Volume Wizard that appears on the screen

Step 8. Enter the desired size for your partition and click Next

Step 9. Select a letter to represent your partition and click Next

Step 10. Indicate whether you want to format the new partition, then click Next

Step 11. Click Done
The SD card will now be partitioned.
Method 2 of 3: Partition SD card on Mac

Step 1. Insert the SD card or card adapter into your computer's USB port

Step 2. Go to the Applications folder and select the Utilities option

Step 3. Select Disk Utility

Step 4. Click on the name of the SD card in the left sidebar of Disk Utility

Step 5. Select Partition at the top of Disk Utility

Step 6. Click the drop-down menu under Current Volume and then choose the number of partitions you want to have on the SD card

Step 7. Click on each partition, then choose a name, format, and size for each
- If you want to use the SD card as a startup disk, select Options, then Score guide.

Step 8. Click Apply. The SD card is now partitioned
Method 3 of 3: Partition SD card on Android device
Warning
For this method, your device must be rooted.

Step 1. Check if the SD card is in your Android device

Step 2. Go to Google Play Store on your Android device

Step 3. Find and download the ClockworkMod ROM Manager application
You can also download ROM Manager from Google Play Store

Step 4. Launch the ROM Manager application after installation

Step 5. Tap Partition SD card

Step 6. Choose the desired size for your partition, next to the Size extension option

Step 7. Select a value next to the Swap Size option, if desired
Swap size is the amount of megabytes that can be used for cache memory to free RAM memory for other programs.

Step 8. Press OK
Your Android device will enter recovery mode and the SD card will be partitioned.

Step 9. Select the restart device option, when prompted
Your card is now partitioned.