How to Add, Delete, and Resize Mac Partitions Without Erasing Them First

Use Disk Utility in macOS to partition your drive

Disk Utility in macOS makes it easy to erase, format, and create partitions on physical storage devices (such as internal and external hard disks); combine multiple hard disks into a RAID set; and repair disk errors. Here, we show you how to resize an existing volume without losing your data as well as add and delete partitions.

Instructions in this article apply to Mac OS X Leopard (10.5.8) and later. Apple upgraded Disk Utility significantly with OS X El Capitan (10.11.6), however, so menus and other names may be slightly different.

Disk Utility on OS X Yosemite (10.10) and earlier operating systems cannot resize or add to an existing volume without first erasing that volume's contents. Do not attempt to use earlier versions of Disk Utility for the process provided here.

How to Resize an Existing Volume

Disk Utility allows you to resize existing volumes without losing data, but there are a few limitations. For example, Disk Utility can decrease the size of any volume, but it can increase the size of a volume only if there’s enough free space available between the volume you want to enlarge and the next volume in that partition.

For practical purposes, this means that if you want to increase the size of a volume, you'll need to delete the volume below it in the partition set. (If the volume is the last one in the set, you won't be able to enlarge it.)

You'll lose all data on the partition you delete, so be sure to back up everything on it first.

To resize an existing partition volume, complete the following steps:

  1. Open Disk Utility, which is located in /Applications/Utilities/.

    Internal drives and volumes appear in the Disk Utility sidebar. Physical drives are listed with a generic disk icon. Volumes are listed below their associated physical drive.

  2. In the sidebar, select the volume you want to resize, then select Partition.

    Disk Utility on macOS Sierra
  3. In the pie chart, select the volume listed immediately below the volume you want to enlarge, then select Delete (the minus sign).

    The pie chart of a macOS Catalina partition
  4. Select Apply. Disk Utility will remove the volume and then move the deleted volume's free space to the volume above it.

  5. In the pie chart, use the line control to move the endpoint of the volume you want to enlarge into the free space.

  6. Select Done.

How to Add a Partition to an Existing Volume

You can use Disk Utility to add a new partition to an existing volume without losing any data. When adding a new partition, Disk Utility splits the selected disk in half, leaving all the existing data on the original disk but reducing its size by 50 percent. If the amount of existing data takes up more than 50 percent of the existing partition's space, Disk Utility will resize the partition to accommodate all its current data, and then create a new partition in the remaining space.

If you're using Apple File System (APFS), Apple recommends not partitioning your disk. Instead, you should create however many APFS volumes you need within the single disk partition.

To add a new partition to an existing disk, complete the following steps:

  1. Open Disk Utility, which is located in /Applications/Utilities/. Current drives and volumes appear in the Disk Utility sidebar under Internal or External, as appropriate.

    Disk Utility
  2. In the sidebar, select a volume, then select Partition.

  3. Select Partition from the pop-up window.

    Disk Utility partition
  4. Select Add (the plus sign). Then, in the Name field, type a name for the new partition.

  5. From the Format list, select the file system format you want to use.

    Depending on the operating system installed on your Mac, three file system formats are available: APFS, which is used by macOS High Sierra (10.13) and later operating systems; Mac OS Extended, used by macOS Sierra (10.12) and earlier; and MS-DOS (FAT) and ExFAT, which are compatible with the Windows operating system. Within each of these file system formats are subcategories, such as APFS (Encrypted) and Mac OS Extended (Journaled).

    Disk Utility partition name
  6. In Size, type a size in gigabytes for the new partition. Or, you can drag the line control between the two resulting partitions to change their sizes.

    To reject the changes you've made, select Revert.

  7. To accept the changes and repartition the drive, select Apply. Disk Utility will display a confirmation sheet that lists how the partitions will be changed.

  8. Select Partition, then select Continue.

  9. When the new partitions appear, select Done. Icons for each partition appear in sidebars of both Disk Utility and Finder.

How to Delete an Existing Partition

In addition to adding partitions, Disk Utility can delete existing partitions. When you delete an existing partition, its associated data will be lost, but the space the partition occupied will be freed. You can use this new free space to increase the size of the next partition up.

When you delete a partition to make room, it's important to understand that partition's location in the partition map. For example, say that you've partitioned a drive into two volumes named vol1 and vol2. You can delete vol2 and resize vol1 to take over the available space without losing the data on vol1. The opposite, however, is not true. Deleting vol1 doesn't allow vol2 to expand to fill the space that vol1 use to occupy.

When you delete a partition, you lose all the data on it. So, be sure to back up everything on it first.

To delete an existing partition, complete the following steps:

  1. Open Disk Utility, which is located in /Applications/Utilities/. Current drives and volumes will appear in the Disk Utility sidebar. Drives have a generic disk icon. Partitions appear beneath their associated drive.

    Disk Utility
  2. In the sidebar, select the partition you want to delete, then select Partition.

  3. Select Partition from the pop-up window.

    Disk Utility partition
  4. In the pie chart, select the existing partition you want to delete, then select Delete. Disk Utility will display a confirmation sheet listing how the partitions will be changed.

  5. Select Apply, then select Partition.

  6. When the partition disappears, select Done. You can expand the partition immediately above the deleted partition by dragging its line control in the pie chart

To make it easier to manage your drives, volumes, and partitions, add the Disk Utility icon to the Dock.