If you don’t have a fancy-schmancy printer that tracks filament usage and warns you if you don’t have enough filament left on the currently-loaded spool to complete the print, this is how you know. You can even double-check while it’s printing, like I do in this video.
This is why you should always keep a kitchen scale and one empty spool of all the filament brands you use.
Low tech but useful. I figured I’d share.
It would be useful to have an “empty spool database” where people post a photo+weight of their empty spool, plus some fancy way to search by image.
Edit: https://github.com/jtrmal/spoolz looks like a partial solution.