How to Calibrate Your Grinder

A great cup of coffee really does start with the grinder. The grinder is the core of any coffee operation, because it determines how consistently your beans are broken down and how much flavour is extracted into the cup. Even the freshest beans and the finest espresso machine cannot make up for a poorly calibrated grinder. Learning how to calibrate your grinder is therefore one of the most important skills for any barista or café owner. 

Calibration begins with an understanding of what you are trying to achieve. The goal is consistency. When beans are ground too coarse, water passes through too quickly, leading to under-extraction and sour, thin-tasting coffee. When the grind is too fine, water struggles to pass through, producing an over-extracted, bitter cup. The perfect calibration creates a balance where the grind size allows water to flow at the right speed, extracting sweetness, body, and aroma.

The process starts with selecting your coffee dose and setting a standard recipe to work from. For example, a common starting point is a ratio of coffee to water such as eighteen grams of coffee yielding thirty-six grams of espresso in about twenty-five to thirty seconds. This provides a baseline against which you can measure outcomes as the recipe slightly fluctuates. Once you pull your first shot, you can taste and observe. If the espresso runs too fast, the grind needs to be finer. If it chokes the machine and drips slowly, the grind needs to be coarser. Each adjustment should be made gradually, as even a small movement on the grinder dial can have a big impact.

Temperature, humidity, and the freshness of the beans all play a role, which is why calibration is not a one-time event. Beans behave differently as they age, and even within a single day you may find the grinder needs tweaks. A humid morning can make the coffee swell and slow extraction, while a hot afternoon can have the opposite effect. For this reason, professional baristas check and recalibrate their grinder many, many times a day to keep flavour consistent.

Good calibration is not just about grind size. Ensuring your grinder is clean and free from old coffee is part of the process too. Oils and residue can build up quickly and interfere with consistency. Regularly emptying the hopper, brushing out retained grinds, and keeping burrs in good condition helps ensure that each adjustment is accurate and that no stale coffee is mixing into the fresh.

The skill of calibration is really about observation and repetition. Over time, you begin to recognise the signs of a shot that is running too quickly or too slowly, and you learn how your grinder responds to adjustments. What seems technical at first becomes second nature.

Ensuring every barista is able to calibrate a grinder properly is essential. It means customers receive the same quality in every cup, no matter who is on shift. It reduces waste, saves time, and keeps standards consistent. Most importantly, it honours the effort that has gone into producing the beans, from farm to roastery, ensuring that flavour potential is not lost at the very last stage.