So my slicer software of choice (Simplify3D) gives me some estimates on filament length for a printed part. That's handy enough but my filament is wrapped around a spool and it's a little bit unclear exactly how long that length of filament that is left is before it runs out.
So... apply math instead.
Weight the spool. (Scale gives me oz but if you have a grams scale that's a good thing.
Full spool is about 43 oz or so. (Multiply by 28.3493 to get grams if you need)
Subtract the weight of an empty spool. I got around 7.7 oz for this.
Result: I have 997 grams of plastic on a full spool. Good they sell in 1kg rolls.
So... how long is that left. Convert grams to volume. You get this from the type of plastic you're using.
If you multiply that and the grams, you can get the volume in for your roll.
Result: Full roll of PLA is about and ABS around .
Lastly, how long is it? You just need to divide by the cross section area of the filament diameter.
So for 1.75mm filament (Lets convert that to cm to keep units the same).
Result: or 340 meters for PLA.