How Do I find my iMac Screen Size
You can find your iMac screen size as per the below.
If your device powers on:
1. Click the Apple icon at the top left of the screen.
2. Click “About This Mac”
3. The device screen size will be stated within the details window as per the image below.
If your device does not power on:
1. The screen is measured diagonally from inside the plastic/metal/glass screen bezel(frame) running around the screen.