Upgrade to Monterey OS

Additionally, 13 GB of empty space will not be enough. You should have a minimum of 20 - 25 GB available at all times - the OS needs room to function properly. And, for Monterey, you will need between 26 to 44 GB of storage for the download and install:

https://support.apple.com/en-us/HT212735

Upgrade to Monterey OS: "Upgrade to Monterey OS: my macbook pro has Catalina macOS. When I try to download Monterey I get a message this update is not available. How do I upgrade to Monterey?[...]"

Verify macOS Compatibility:

A. Start Here: Learn About Compatibility and how to Identify your Specific Mac Model - Apple Support

B. How to Verify:

I. Reveal your Model:

What is the Model of your Mac? To find out...

1. Go to: Apple menu
2. Click: About this Mac
3. View: Second Line-Down

then...

II. Compare the Results:

See if the Model you found is shown here:

• macOS Monterey is Compatible with these Computers - Apple Support

III. If Compatible:

• Back Up your Mac First:  Be certain you Create a Time Machine Backup of your Mac, so that way you can have something to restore your Mac from, should anything go wrong with the reconfiguration.

Upgrade to Monterey OS: "[...]Do I have to upgrade to Big Sur first, and then to Monterey? Will it require say 12gb for big sur and another 12gb for Monterey upgrade? I have barely 13 gb space left on HD"

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No. You do not have to upgrade to Bug Sur first. Remove large items (i.e. Movies, TV Shows, and Virtual Machines), if you want to save space. Once removed, restart your Mac, and then proceed with the upgrade.

Back Up your Mac First:  Be certain you Create a Time Machine Backup of your Mac, so that way you can have something to restore your Mac from, should anything go wrong with the reconfiguration.

Hi,

Monterey is required MacBook pro mid 2015 or later. If your MacBook Pro suites it, you can upgrade to Monterey from System Preferences > Software update.