If you can run Sierra, then your machine is compatible with High Sierra. See the following list for Mojave compatibility:
MacOS Mojave Compatibility List of Supported Macs
Apple has said that any Mac introduced in mid-2012 or later will support macOS Mojave, along with the 2010 and 2012 Mac Pro models if they have a Metal capable GPU. That’s fairly descriptive, but if you want a specific list of supported Mac hardware for macOS Mojave 10.14 then the following should be helpful to you:
- MacBook Pro (mid-2012 and newer)
- MacBook Air (mid-2012 and newer)
- MacBook (early 2015 and later)
- iMac (late 2012 or newer)
- iMac Pro (2017 or newer)
- Mac Pro (late 2013 or newer, or mid-2010 and mid-2012 models with Metal capable GPU)
- Mac Mini (late 2012 or newer)
As you can see from the list, basically every Mac that was introduced from mid-2012 onward supports macOS Mojave, along with a few earlier Mac Pro models. The supported hardware list for macOS 10.14 is a bit more restrictive than prior macOS system software releases, perhaps indicating that the latest software version will be more demanding on resources or simply just require particular system architecture components that are only available on more modern Macintosh hardware.
Get MacOS Mojave now from the Mac App Store
Be sure your disk is functioning properly and that you have no problems with your Sierra system. Otherwise, you will want to erase the drive before upgrading.
In the future please read Writing an effective Apple Support Communities question.
We are here to help. We are all users. We are not mind-readers nor clairvoyants. We only know what you write down and tell us. Be specific and thorough. Include your hardware information and installed version of macOS.
