Grind size is a dial, not a setting
Every grinder review ends with a table of "recommended settings". I have stopped trusting them. Two grinders of the same model can be a few clicks apart, burrs wear in, and a light roast from Kenya behaves nothing like a dark roast from Brazil.
What works better is treating grind size as something you steer while you brew, using two signals you already have: how long the brew takes and how it tastes.
Read the cup
- Sour, thin, a bit salty — under-extracted. Grind finer.
- Bitter, dry, hollow at the finish — over-extracted. Grind coarser.
- Sweet, with a finish that lingers — leave it alone and write the setting down.
Move in small steps
Change the grind by two or three clicks at a time and keep everything else fixed: same dose, same water, same pour. If you change the ratio and the grind at once, you will never know which one helped.
A brew that is a little too fine is usually easier to drink than one that is a little too coarse.
Use time as a sanity check
For a 15 g V60 I expect the water to drain somewhere around 2:45–3:15. If it finishes at 2:00, I am almost certainly too coarse; if it is still dripping at 4:00, the bed is probably clogged with fines. Time does not tell you whether the coffee is good, but it tells you when something is far off.
Write it down
A strip of masking tape on the grinder with the bean name and the click number has saved me more coffee than any gadget.