ALWAYS SPEC every roll of your filament(s). 1.75mm is just the standard,, not the actual size. Every spool will vary,, and dialing this in to the nearest 1,000th (eg: 1.7xx) in your slicer profile for that print, will show big improvements.
- use digital calipers
- measure 2x @ 90* angle, in each spot (bump it twice, to make sure you are getting the same reading)
- measure about 10-15ft,, every 2ft
- average out the specific #.. write that # on the side of spool, for future reference.
- you should do this several times per spool. Say... every 250-300g
There are lots of other variables you'll learn,, material - temperature - speed - cooling - object geometry,, and that where the ART of printing becomes the challenge for improving print quality.. But always start with a specific diameter.