How to dial in an espresso grinder?

Dialling in an espresso grinder means finding the exact grind setting that produces a balanced espresso within the target extraction time — typically 25 to 35 seconds for 18 g of coffee yielding 36–40 g of liquid. If the shot runs too fast (< 20 s): grind is too coarse, go finer. If too slow (> 40 s): grind is too fine, go coarser. Each adjustment should be made in small increments, and the grinder must be purged after each change to avoid mixing two different grind sizes.

Dialling in is the daily or weekly procedure that allows any barista to maintain consistent espresso quality. It is made necessary by two factors: coffee ageing (a bag opened 3 weeks ago extracts faster than freshly opened beans, since CO2 degassing is complete) and variations in ambient temperature and humidity (which slightly change the coffee's absorption properties).

The first step is to establish reference parameters. For a standard espresso, the baseline recipe is: 18 g of coffee in (dose), 36–40 g of coffee out (extracted liquid weight), in 28–32 seconds, at 9 bar, at approximately 93 °C. This 1:2 ratio (dose:liquid) is a starting point, not an absolute rule. Some modern recipes use ratios of 1:2.5 or even 1:3 for light roasts.

The concrete procedure starts with a calibration pull. Without changing the grind, pull a first shot and observe: flow time, stream colour, crema texture. If the shot runs in 20 seconds with a pale, watery stream = too coarse. If it trickles for 45 seconds with very little liquid = too fine. Adjust by one or two steps in the appropriate direction, purge the transition (about 2–3 g of coffee to flush old grind from the path), and pull again.

Tasting is essential at each step. The time may be in window but the coffee can still be sour (under-extracted) or bitter (over-extracted). Learning to read both pieces of information together — time + taste — is the core skill. Correct time with sour taste often indicates consistent grind but temperature too low, or a light roast that needs a finer grind than the time window alone would suggest.

Stepped-adjustment grinders require discrete moves — one step corresponds to a variation of a few to a few dozen microns depending on the grinder. Stepless grinders allow infinitely fine adjustments, more precise but harder to memorise. Keeping a log of grind settings (on paper or in an app) is essential for any barista working several different coffees or returning after a break.

Dial-in diagnostic: reading an espresso shot