Grind size is the variable that influences your espresso the most — more than brew temperature, more than tamping pressure, more than the machine. Yet "how fine do I need to grind?" is the question that has no universal answer. We explain why that is, how you find your grind size, and what you can do if it doesn't taste good. (You'll find the basics of espresso preparation in our preparation guide.)
Why there's no magic number
"Set your grinder to 12" is a sentence you constantly read in forums. The problem: Setting 12 on your grinder produces a completely different particle size than setting 12 on a grinder of the same model. Even two identical grinders from the same factory can grind differently coarse at the same setting. The grinding burrs sit slightly differently, the calibration varies, and usage has worn the burrs differently.
Grind size is therefore not a numerical value you can transfer. It's a setting that you have to find yourself for your grinder, your coffee, and your machine. The good news: It's less complicated than it sounds.
The method: Finding the right grind size through time
You need three things: A scale, a stopwatch (or a scale with timer), and a recipe as a starting point. Let's take the standard recipe: 18 g coffee, 36 g espresso in the cup, time window 25–30 seconds.
Dose 18 g coffee, tamp, pull the shot, and observe two things: how many grams land in the cup and how long it takes. The extraction time tells you whether the grind size is right.
If the espresso runs through too quickly (e.g., 36 g in 18 seconds), the grind size is too coarse. The water encounters too little resistance and rushes through the puck. The espresso typically tastes sour, thin, and watery.
If it runs too slowly (e.g., 36 g only after 40 seconds), the grind size is too fine. The water barely gets through, the coffee becomes over-extracted. The espresso tastes bitter, astringent.
If you land in the time window (25–30 seconds for 36 g), you're in the right range. From here on, your taste decides.
Adjusting grind size: How much to turn?
Here's the rule: less than you think. With most espresso grinders, small turns make a noticeably significant difference. With some grinders with fine adjustment (e.g., the Eureka Mignon or the Niche Zero), it's even just one or two click stops or marks. How finely the grind size can be adjusted is itself a buying criterion when you're thinking about which grinder you need.
The rule of thumb: Adjust the grind size in small steps and pull a shot after each change. Don't jump from "way too coarse" straight to "extremely fine" — you'll almost always overshoot, and especially when you set it noticeably finer, the grinder can even clog. A good rhythm: One small adjustment, one shot, taste, correct. After three to four shots, you're usually in the right range.
Important: After adjusting, discard the first small amount of ground coffee (2–6 g is usually enough). There's still coffee powder in the burr chamber from the previous grind setting. If that gets into your portafilter, it will skew the result. We call this coffee residue retention and it varies in size from grinder to grinder.
When you need to readjust the grind size
Grind size is not a set-and-forget setting. Several factors change how the coffee behaves at the same grind size:
New coffee: Each coffee has a different density, cell structure, and roast. When you open a new bag — even of the same coffee — the grind size can be slightly off. With a completely different coffee (e.g., from light to dark roasted), you often need to adjust several settings.
Age of the coffee: Freshly roasted coffee releases CO₂. In the first days after roasting, it resists the water more strongly, the shot runs slower. At the same time, it bubbles and isn't delicious yet. We recommend starting to prepare espresso about two weeks after roasting. The longer the coffee sits, the finer you'll need to grind it over time.
Humidity: At high humidity, ground coffee swells easily and creates more resistance. On humid summer days, your espresso can suddenly run slower, even though you haven't changed anything. One setting coarser usually solves it.
When your espresso tastes sour — despite fine grind size
A common problem: The espresso tastes sour, so you grind finer. And finer. And at some point the shot takes 40 seconds and still tastes sour. What's going on?
Usually channeling. When the grind size is very fine, but the coffee puck wasn't distributed evenly, pressure builds up unevenly. The water finds a channel through the puck and extracts everything there (bitter), while the rest of the puck barely gets any water (sour). The result is an espresso that tastes both sour and bitter at the same time, no matter how fine you grind.
The solution then isn't in the grind size, but in the preparation of the puck. Distribute the coffee in the portafilter evenly (WDT with a needle works well), then tamp evenly. More on this in our preparation guide. A pre-infusion can also help with channeling because it saturates the puck more evenly before full pressure arrives.
If none of that helps and the espresso still tastes sour at the right time and ratio, the brew temperature might play a role. Temperature that's too low extracts fewer acid-binding compounds. Two to three degrees more can make the difference. But try grind size and puck preparation first — that solves 90% of the problems.
Espresso grind size vs. filter coffee grind size
Espresso requires the finest grind size of all brewing methods. For comparison: filter coffee is ground about like fine sand, French press like coarse sea salt. Espresso is somewhere between powdered sugar and fine sand — noticeably finer than anything else.
This has a simple reason: Contact time in espresso is only 25–30 seconds. For the water to extract enough flavor from the coffee in this short time, the surface area of the coffee particles needs to be as large as possible. Fine grind size = more surface area = more extraction per second.
That's why you need a grinder for espresso that can grind fine enough and delivers a uniform particle size. Not every coffee grinder achieves this. A decent espresso grinder costs around 200 euros and up. Cheaper grinders can grind fine, but unevenly — with many coarse and many too-fine particles at the same time. This leads to under- and over-extraction in the same shot. Which grinders manage this, our comprehensive espresso grinder test shows. A curated selection of recommended grinders can be found in the espresso grinder selection. Hand grinders in the affordable range under 100 euros are often the best choice.
Setting grind size: Reaching your goal in five shots
If you have a new grinder or want to start a new coffee, this method will get you to your goal quickly. Define the recipe or use our recipe. We provide a recipe for each espresso in our shop.
Shot 1: Start with a setting that seems roughly right to you. Dose 18 g, pull to 36 g, and stop the time. If the shot takes under 20 seconds: grind noticeably finer. Over 35 seconds: grind noticeably coarser.
Shots 2–3: Correct in the right direction, each time in small steps. You should now land in the range of 22–32 seconds.
Shots 4–5: Fine-tuning. Small corrections, taste, enjoy. If the espresso is in the time window and tastes good to you: done. If it's in the time window but doesn't taste good: Keep reading at Espresso too sour or adjust the brew ratio (slightly more or less water).
Yes, it costs you five shots of coffee. Think of it as an investment — after that, you'll know where your grinder stands, and you'll only need to make minor adjustments.
More on brew time and why it's your most important diagnostic tool: Espresso extraction time: When does the brew time really start?
Your espresso tastes sour? Then check out our detailed troubleshooting article: Espresso too sour — what to do?
