How do you dial in an espresso?

Dialing in an espresso is the systematic process of adjusting extraction parameters — primarily grind size, dose, ratio, and brew time — to reach a target cup profile that is measurable and reproducible. It works by changing one variable at a time and evaluating the impact on taste and/or TDS (Total Dissolved Solids) after each iteration. A thorough dial-in extracts the best possible result from a given coffee batch on a specific machine and grinder, under the prevailing temperature and humidity conditions.

Every dial-in starts with a reference point. Experienced baristas typically begin with a 1:2 to 1:2.5 ratio (e.g., 18 g of coffee to 36-45 g of liquid) and a target extraction time of 25 to 30 seconds. If the machine has a flow meter or pressure gauge, the first check is that pressure during extraction is stable at 9 bars (or the chosen pressure profile). From there, the logical dial-in sequence moves through three levels: coarse adjustment, fine adjustment, and micro-adjustment.

At the coarse level, grind size is adjusted until the target time is reached. A grind that is too fine produces extraction times above 35 seconds with a very slow, restricted flow — the resulting espresso is typically bitter and astringent. A grind that is too coarse produces extraction below 20 seconds with fast, watery flow — the result is sour, hollow, and under-extracted. Adjustments are made in grinder steps, and a useful rule of thumb is that one step changes extraction time by 2 to 5 seconds, depending on the grinder and the coffee.

At the fine level, the yield (weight of liquid collected) is adjusted. Once the time target is hit, if the espresso still tastes too strong or concentrated, the yield is increased (e.g., from 36 g to 42 g) to dilute slightly. If it tastes weak or thin, the yield is reduced. For objective measurement, a refractometer reads TDS: specialty espresso typically falls between 8 and 12% TDS, with an extraction yield (EY) of 18 to 22%.

Micro-adjustments involve finer levers: brew temperature (±1-2°C), pre-infusion duration and pressure, coffee distribution in the portafilter (WDT — Weiss Distribution Technique or a distribution tool), and tamp pressure. These parameters have a smaller impact than grind and ratio, but become decisive once everything else is optimized. A frequently overlooked fact: ambient humidity directly affects ground coffee density and hydraulic resistance — on rainy or humid days, the grind often needs to be opened by one step to compensate for moisture absorption by the beans.

Dial-in sequence: symptoms, causes, and corrections