How to Choose the Perfect Boot Camp Partition Size to install Windows for Mac

The operating system will take up a good portion of it (likely around 30-45 GB), as well as requiring a decent chunk of free space for updates and other Windows functions. I really wouldn't allocate any less than 64 GB to Windows (though with a 1 TB internal SSD, I'd go for 128 GB), and that's only if the software you need isn't more than a couple GB in size. If you even think you might need more in the future, it's best to do it now- if you need to allocate more space later, you'll have to erase the Windows partition and go through the setup process again.

Why not install Windows into a Virtual Machine instead if all you need to do is access a printer? Dual booting is a pain because you have to reboot to move between the two operating systems. Plus partitioning a drive is always risky because most people discover one or both partitions don't have enough Free space.

Running Windows in a Virtual Machine means you launch the Virtual Machine with Windows like a standard macOS app. While the VM & Windows are running, your system will need to share resources such as CPU cycles & memory, but you can just close down the VM & pause Windows so you can relaunch Windows fairly quickly without needing to reboot macOS.

Just make sure to check the Recommended system requirements for your printing software to be sure running Windows in a VM will be sufficient for the task.

If you choose to use Bootcamp, then make sure you have a good backup of your macOS data just in case you need to erase the computer to fix any partition issues with the system.

Or maybe invest in a standard Windows PC for this purpose. Keep in mind if you use a new Apple Silicon M-series Mac, that running Windows on bare metal will not be an option so you may want to consider finding a solution now which will allow you use an Apple Silicon Mac later on without impacting your workflow. Just something to consider anyway.

I would allocate 70% for Windows. There are more programs for it.