The likely problem is that you do not have a 40GB contiguous block of free space due to some fragmentation. Back up your macOS volume by cloning it to another drive. Then erase your drive and install macOS from your cloned backup. Then you should be able to set aside the 40GB volume for Windows. Be aware that you will only have 7GBs of free space for macOS. You need to maintain a minimum of 20GBs or 10% of the startup drive's capacity, whichever is greater.

Boot Camp Assistant Not Enough Space On Large Disk Storage

A 120GB SSD is not large enough to run macOS and Windows comfortably without worrying about running out of space.

Jan 1, 2019 8:50 PM

Boot Camp Assistant Not Enough Space On Large Disk Space

Boot Camp Assistant Not Enough Space On Large Disk Hard Drive

Boot Camp Assistant Not Enough Space On Disk

Disable time machine. Go to the System Preferences and click the Time Machine. Then untick the BackUp automatically and close the dialog. Then open the terminal and run following command. Sudo tmutil thinlocalsnapshots / 99. Then restart the machine. Then try to run Bootcamp and most of the times issue get solved by this method. Answers It is possible that there is not enough free space in a single congruent area on your SSD - meaning that fragmentation is keeping you from being able to partition. In that case, you can either try to find a utility that will defrag, or back up to another drive, reformat, partition, then restore.