Purge Command to free up Memory

How to free up inactive memory in OSX using Purge command – Open Terminal then type ‘purge.’ This will clear out inactive memory. Launch Terminal, found in /Applications/Utilities/ and enter the following command ‘purge.’ Give OS X a minute or two to complete the process. If you want to see what the results of this command does to help, then before doing this, open up Activity Monitor to see the used system memory. Run the purge command, then open activity monitor once again to see the changes.

Images below to walk you through doing this command via terminal.

First step, open Activity Monitor to see where your current machine is on memory usage.

You can find both Activity Monitor and Terminal by going to your Applications folder then to Utilities folder, or by opening Spotlight and typing the name of the application you’re looking for.

Once you have opened Terminal, type this command. It’s a one word command so no need to let it scare you. Type without the quotations ‘purge’ then hit enter.

You will see your Home folder name drop down one line. That’s how you will know that the command has finished its process. I won’t bore you with what is being done in the background. Just know this is the quickest way to clean your memory usage without installing a third party application.

Close Terminal open your Application folder then Utilities.

From the Utilities folder, open Activity Monitor.

You can now view Activity Monitor to see the changes made by the Purge command.
 UPDATE: if you are looking for this to work in Mavericks you will need to follow these instructions. Purge for Mavericks