How do I dial in a new bag of coffee?

Dialling in is a search with one variable. Keeping everything else fixed is what makes it fast.

Set the constants

Dose — whatever your basket is designed for. 18 g in an 18 g basket. Ratio — 1:2 to start. 18 g in, 36 g out. Temperature — 93 °C, or whatever your machine gives.

Weigh the input and the output. Every time.

Then move only the grind

Pull a shot. Note the time.

Under 22 seconds and sour — grind finer. Over 35 seconds and bitter — grind coarser. 25 to 32 seconds — taste it and decide.

Move in small steps. Most grinders need only a click or two.

Then taste, not time

Once you are in range, time stops being the guide.

Still sour — finer, or hotter, or go longer to 1:2.5. Bitter and drying — coarser, or cooler, or stop at 1:1.8. Thin and hollow — often needs a higher dose or a finer grind.

Purge between changes

A grinder holds grounds from the previous setting. Run a few grams through and discard before judging a change.

Expect to redial

Same bag, one week later, is a different coffee. Small adjustments as it ages are normal, not a failure.

For filter

Same logic, fewer shots. Grind is still the main lever, ratio stays fixed at 1:16.