DIALLING IN: A BEGINNER'S GUIDE TO GRIND SIZE AND EXTRACTION
Barista Skills — 1 July 2026
Every barista starts their shift by dialling in the grinder. Here is what that means, why it matters, and how you can apply the same thinking to your home setup.
Every morning, before the first customer walks through the door, every Chambers barista does the same thing: they dial in the grinder.
Dialling in is the process of adjusting the grind size until the espresso extracts within the correct parameters — typically a ratio of 1:2 (one gram of coffee producing two grams of liquid espresso) in a time of twenty-five to thirty seconds. It sounds simple. It is not. The correct grind setting changes every day, sometimes every hour, as temperature, humidity, and the age of the coffee affect how the grounds behave under pressure.
Understanding extraction is the foundation of understanding coffee quality. Extraction refers to the percentage of the coffee's soluble compounds that are dissolved into the water during brewing. Under-extraction — pulling too little from the coffee — produces a cup that is sour, thin, and lacking sweetness. The acidic compounds extract first; if you stop the process too early, that is all you get. Over-extraction — pulling too much — produces a cup that is bitter, harsh, and astringent. The compounds that extract last are the ones that taste unpleasant.
The ideal extraction window — where the cup is balanced, sweet, and complex — sits between approximately 18% and 22% of the coffee's total soluble mass. Achieving this consistently requires controlling the variables that affect extraction rate: grind size, water temperature, dose, and time.
Grind size is the most powerful of these variables. A finer grind increases the surface area of the coffee exposed to water, which speeds up extraction. A coarser grind reduces surface area and slows extraction. This is why different brew methods require different grind sizes: an espresso machine forces water through the coffee in twenty-five seconds, so it needs a very fine grind to extract enough in that time. A French press steeps for four minutes, so it needs a coarse grind to avoid over-extraction.
For home espresso, the dialling-in process works like this: pull a shot and taste it. If it is sour and thin, grind finer — you are under-extracting. If it is bitter and harsh, grind coarser — you are over-extracting. Adjust in small increments and taste after each change. Keep notes. The correct setting for a given coffee on a given day is specific; what worked yesterday may not work today.
For pour-over and other filter methods, the same principle applies, but the feedback loop is slower. If your pour-over tastes sour, grind finer or extend your brew time. If it tastes bitter, grind coarser or shorten your brew time. The goal is always the same: a cup that is balanced, sweet, and complex, with no single flavour dominating.
Dialling in is not a one-time task. It is an ongoing conversation between the barista and the coffee. The baristas who do it best are the ones who taste constantly, adjust confidently, and never stop paying attention.