Grind Size
Grind size controls surface area and flow. Finer grinds extract faster and slow water down. Coarser grinds extract slower and let water pass more easily.
Why grind size matters
Grinding breaks coffee into particles. Smaller particles expose more surface area, so water extracts flavor faster.
Grind also changes flow. Fine grinds pack together and slow water. Coarse grinds leave larger gaps and let water pass faster.
Common grind ranges
Extra coarse is used for some cold brew. Coarse is common for French press. Medium-coarse to medium works for many immersion brews. Medium-fine is common for pour-over. Fine is common for AeroPress and espresso-like recipes. Espresso is very fine.
These names are rough. One grinder's medium can be another grinder's medium-fine.
How taste tells you where to move
If the coffee tastes sour, salty, grassy, sharp, or thin, try grinding finer or increasing brew time.
If it tastes bitter, dry, harsh, woody, or muddy, try grinding coarser or reducing agitation.
Do not change everything
When dialing in, keep dose, water, temperature, and recipe the same. Change grind by a small step, brew again, and taste.
Grind is usually the first variable to adjust because it has a strong effect and is easy to repeat.
Quick reference
Finer
More extraction, slower flow, more body.
Coarser
Less extraction, faster flow, more clarity.
Too fine
Bitter, dry, muddy, clogged.
Too coarse
Sour, sharp, thin, fast.