Viewing Mac OS X memory usage and installed RAM

Learn how check the amount of installed RAM (physical memory) and the amount of memory being used.

This article has been archived and is no longer updated by Apple.

To see how much RAM is installed, choose About This Mac from the Apple Menu. The Memory field specifies the amount of RAM installed in the computer.

Mac OS X does not display the memory allocation and usage levels of individual applications in the About This Mac Window. Mac OS X automatically manages memory allocation and usage. This is different from earlier versions of Mac OS.

Viewing memory usage

  1. For Mac OS X 10.3, 10.4 or later, open Activity Monitor (/Applications/Utilities/). For Mac OS X 10.2.8 or earlier, open ProcessViewer (/Applications/Utilities/).
  2. Mac OS X processes and applications are listed in main window. In Mac OS X 10.3.9 and earlier, the "% Memory" column indicates the percentage of RAM in use by an application or process at the time of sampling.

    In Mac OS X 10.4 or later, you can see the overall percentages of memory in use or idle at the bottom of the Activity Monitor window.


Advanced users might prefer to use Terminal. Please see Mac OS X: How to View Memory Usage With top.


  1. In Mac OS X 10.2.8 or earlier, if 2.0 GB RAM is installed, usage is not correctly reported. See this document.
  2. It is normal for some processes to use very little RAM at times, such as 0.0% or 0.1%.
  3. It is normal for a process' memory usage to change dramatically from one sample period to another, depending on how you are using your computer.
  4. Not all application names in the Process Listing window are easily recognized. For example, Microsoft Internet Explorer 5.1 may appear as "LaunchCFMApp." This is normal.
  5. Classic applications do not appear individually in the Process Listing window. The Classic environment appears as a single process (TruBlueEnvironme). This is normal. See Note 6.
  6. ProcessViewer itself is listed because it is an open application. This is normal.
  7. In Mac OS X 10.2 or later, The Memory/Versions section of the Classic preference pane displays information about the Classic environment similar to what is displayed by Mac OS 9 when you select About this Macintosh from the Apple menu. A scrolling list of active Classic applications and their memory usage is displayed, and a checkbox controls whether background-only applications will appear in this list. It also displays information about the installed versions of the Classic environment.
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