How to Set the Grind Size for Espresso
Grind size is the dial you turn most often when making espresso. Here you’ll learn how to find it systematically, why it shifts with every bean and even from day to day, and how to recognise faults by taste.
Why grind size decides so much
The finer you grind, the larger the surface area of the coffee and the denser the grounds sit in the basket. The water takes longer to pass through the puck and dissolves more on its way. Coarser grounds let the water through faster, so extraction is lower. No other brewing method is as sensitive to this as espresso, because contact time and the amount of coffee are so small.
That is why the right grind size can’t be set once and then forgotten. It depends on the bean, its roast level, its age, your dose and even the humidity.
Shot time as your compass
Keep dose and yield fixed, for example 18 g of coffee and 36 g of espresso, a ratio of about 1:2. Grind size is then the only variable, and the time shows you where you stand. As a guideline, aim for about 25 to 30 seconds from pump start. If the shot runs much faster, grind finer; if it takes much longer, grind coarser.
Time is a compass, not a goal. Some light roasts taste lively and clear at 22 seconds, some dark ones are roundest at 32 seconds. Use the clock to get into the right range, then let your palate decide. The full recipe with dose, temperature and workflow is in our portafilter espresso guide.
How to dial in
- Start with a medium espresso setting or the last setting that worked with a similar bean.
- Pull a shot with a fixed dose and a fixed target yield and note the time.
- Adjust the grinder by one small step in the right direction.
- After adjusting, grind a few grams and throw them away, so no old grounds from the grinder end up in the next shot.
- Pull the shot again and compare time and taste.
- Once the time is in the target range, taste carefully: if it is balanced, you’re done. If not, adjust in even smaller steps.
Small steps are the key. On many espresso grinders even a tiny turn shifts the time by several seconds. Stepless grinders allow especially fine corrections, while stepped grinders sometimes need a compromise between grind size and dose. If you land between two steps, you can adjust the dose by half a gram.
Roast level and bean age
Light-roasted beans are denser and release their aromas less easily. They usually need a finer grind, often also a higher temperature or a slightly longer ratio such as 1:2.5. Dark-roasted beans are more porous and more soluble. At the same grind size they run faster but also turn bitter sooner, so you usually grind coarser than for a light roast.
As beans age they lose carbon dioxide. When freshly roasted, the gas slows the water flow and the shot tends to run slow and uneven. Over the following weeks the same coffee runs faster and faster at the same setting. If you use up a bag over two or three weeks, you’ll therefore grind gradually finer. Even a freshly opened bag of the same coffee can need a new setting.
Store your beans airtight, dark and at room temperature, and buy smaller amounts. That keeps your grind setting more stable over time. You’ll find an overview of different roasts in our espresso collection.
Symptom, cause, correction
| Symptom | Likely cause | Correction |
|---|---|---|
| Shot under 20 seconds, pale and thin | Grind too coarse | Grind clearly finer |
| Sour, salty, short finish | Under-extraction | Grind finer or increase the yield slightly |
| Shot over 35 seconds, only drips | Grind too fine | Grind coarser |
| Bitter, dry, furry on the tongue | Over-extraction | Grind coarser or reduce the yield |
| Good time, but sour and bitter at once | Uneven extraction, channeling | Improve distribution and tamping, don’t touch the grind size |
| Time varies a lot from shot to shot | Changing dose or old grounds in the grinder | Weigh every dose, purge briefly after adjusting |
| Right yesterday, too fast today | Beans older, climate changed | One small step finer |
The table shows typical relationships, not fixed rules. Always check first that dose and yield are right before you change the grind size.
Common mistakes when dialling in
- Changing several things at once: if grind size and dose shift together, you don’t know what made the difference.
- Jumps that are too big: going straight from far too fast to far too slow means you circle around the target for a long time.
- Judging by the clock alone: a shot in 28 seconds can still taste unbalanced.
- Not purging after adjusting: the first shot then still contains grounds from the old setting.
- Ignoring the manufacturer’s advice on adjusting: some grinders should only be set finer while the burrs are running, so beans don’t get stuck between them.
Train your palate on purpose
A helpful exercise: pull three shots of the same bean at three different grind sizes, one too coarse, one right, one too fine, and taste them side by side. You’ll quickly learn how acidity, sweetness and bitterness shift. In the Rocademy at our café in Maxvorstadt you can taste comparisons like these right at the bar.
Sources
Frequently asked questions
How often do I need to adjust the grind size?
With every new bean, and often over time with the same bag too. A quick test shot in the morning shows whether you need to readjust.
Why does fresh coffee run slower?
Freshly roasted beans contain a lot of carbon dioxide. The gas slows the water flow. The more of it escapes, the faster the shot runs at the same setting.
Can I change the grind size instead of the dose?
Yes, that is actually the usual approach. Keep the dose fixed to suit the basket and control the time with the grind size. The dose is better suited to fine corrections.
Does pre-ground coffee work in a portafilter?
Only to a limited extent. You can’t adjust the grind size, and ground coffee quickly loses aroma and carbon dioxide. For consistent results, your own grinder is the better choice.
