Filament spool ruler

This is a simple measurement tool for measuring how much filament is left on a spool measured in grams and percentage. You hold the ruler on the inside of the spool touching the filament with the edge of the ruler. Where the outer edge of the spool hits the ruler is how much is left on the spool.

It's only made for 1kg spools with 750g of filament, with an total outer diameter of 200mm, and an inner diameter of 106mm.

Printing orientation depends a bit on the printer quality, but in general I would recommend printing it laying down with the numbers up.

And I know there's a ton of different spool dimensions out there, so I hope this can inspire some of you to make your own versions for the types of filament spools you use.
A few tips if you want to try it: Make a formula based on the area of filament visible from the side of the spool, and rewrite it to express a radial measurement measuring from the outer edge and inwards.
The final equation should look something similar