How to Change the Screen Resolution on a 27" iMac

By Andrew Tennyson

You can also adjust the resolution of external displays connected to your iMac.
i Kevork Djansezian/Getty Images News/Getty Images

Your iMac features a high-definition screen that you can set to several different resolutions using the computer's System Preferences panel. Changing the resolution may prevent some applications from fitting entirely on your screen and can therefore limit your access to menus and other on-screen functionality.

Step 1

Click the "Apple" menu in the upper-left corner of your screen and select "System Preferences" to load your iMac's System Preferences panel. The Apple menu is identified by a small Apple logo. System Preferences is the location on your Mac where you customize computer settings.

Step 2

Click the "Displays" icon to load the Displays settings panel. The Displays icon resembles a computer screen and is located in the second group down on the System Preferences panel.

Step 3

Click the "Display" tab if it is not already selected and then click the "Scaled" radio button. If you have never changed your display settings in the past, your iMac will have "Best for display" selected by default, but you need to select Scaled to change the resolution from the native resolution.

Step 4

Select the resolution you want to use from the list of available resolutions and then wait for the iMac to reset the display. It should take no longer than 15 seconds for the iMac to automatically recalibrate itself.