High Sierra upgrade stuck at "Installation is in progress. Calculating time remaining..."

If you don't have a backup, this Fix worked for me and got me back up and running (after being stuck at a black screen with apple and status bar) :

1. Get an External Hard Drive the same size or larger than your internal drive. It should be empty so first backup and delete any files on the external drive.
2. Start up in Recovery Mode (CMD + R).
3. Open Disk Utility and Erase your external drive. *Make sure you select the external drive and not your internal drive.Format should be Mac OS Extended Journaled. Close Disk Utility.
4. Back at macOS Utilities, Click on Reinstall macOS and install a new copy of High Sierra on the external drive.
5. Once that completes, Migration Assistant will ask you if you want to migrate. SelectFrom a Mac, Time Machine backup, or startup disk and select your internal drive. (This will take a long time, in my case 5-8 hours for 1 TB SSD)
6. Once migration completes, it should boot into the external drive and you will see your desktop. If you got this far, Reboot back into Recovery Mode (CMD + R).
7. Open Disk Utility and Erase your internal drive this time.
8. Back at macOS Utilities, Click on Reinstall macOS and install a new copy of High Sierra on the internal drive this time.
9. Once installation completes, it will ask again if you want to migrate. Select From a Mac, Time Machine backup, or startup disk and now select your external drive. (This will take a long time again)
10. Once migration completes, you should be good to go!

Good luck!

artsigns.com

Although High Sierra takes a bit longer to install than

previous system upgrades, 3 hours+ does seem a bit long.

There have been a few folks that claim to have powered down

and powered back up and the install resumed and finished shortly

there after.

You could try, but caution you that it may bork the machine and

you may have to go through a recovery process.

One reason why I prefer creating clones rather than Time Machine.

You can immediately boot back up to a machine in its previous

state and sort things out or just reformat and clone back.

I had this problem with my iMac, after wiping the drive. After close to an hour it started and finished the installation. Phew. My data was backed up.

I had this problem on my MBAir, after wiping the drive. After several hours it hadn't progressed. I powered off and back on. Clearly the OS was broken, as all I saw on the display was a lot of hex code and code about the kernel. I then tried the Internet recovery. That worked. It intermittantly toggled between calculating and installing. I was able to wipe the drive and the installer completed as I am sure Apple engineering had hoped for.

With the stuck machine I shut it down. I then booted to Internet recovery mode: power on and hold option-command-R keys simultaneously. That will begin the installation from Apple's recovery server. You need Internet access. If you're not on Ethernet it will ask to select a wireless access point, and you will have to prove the WiFI password for that access point. That worked for me.

First, did you do any sort of system backup before you started?

Thanks for posting this. I had exactly the same problem - I left my computer overnight, but it was still stuck trying to install High Sierra (16+ hours). Following your steps solved the problem.

What happens if I don't have a backup? Will all the data be erased?

Machine in Stuck while installing macOS High Sierra. Its being 14 Hours.

What to do?