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 a 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 type. Even two identical grinders from the same factory can grind differently coarse at the same setting. The burrs sit slightly differently, calibration varies, and use has worn the burrs differently.
Grind size is therefore not a numerical value you can transfer. It's a setting you need 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 timing
You need three things: A scale, a stopwatch (or a scale with timer), and a recipe as a starting point. Let's use 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 your grind size is correct.
If the espresso runs through too quickly (e.g., 36 g in 18 seconds), your grind is too coarse. The water finds 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), your grind is too fine. The water barely gets through, and the coffee becomes over-extracted. The espresso tastes bitter and astringent.
If you land in the time window (25–30 seconds for 36 g), you're in the right range. From here, your taste decides.
Adjusting grind size: How much do you turn?
Here's the rule: less than you think. With most espresso grinders, small turns make a noticeably significant difference. With some grinders that have fine adjustments (e.g., the Eureka Mignon or Niche Zero), it's just one or two clicks or notches. How finely you can adjust the grind size 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 if you adjust significantly finer, the grinder can even clog. A good rhythm: make one small adjustment, pull a 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 ground coffee from the previous grind size in the burr chamber. If that gets into your portafilter, it falsifies the result. We call this residual coffee retention, and it varies in size from grinder to grinder.
When you need to adjust 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: Every 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.
Coffee age: Freshly roasted coffee releases CO₂. In the first days after roasting, it resists water more, and the shot runs slower. At the same time, it's still bubbling and doesn't taste good yet. We recommend waiting a good two weeks after roasting before starting to make espresso with a coffee. The longer the coffee sits, the finer you need to adjust it over time.
Humidity: In high humidity, ground coffee swells slightly and creates more resistance. On muggy summer days, your espresso can suddenly run slower even though you haven't changed anything. Going one setting coarser usually solves it.
When your espresso tastes sour — despite a fine grind
A common problem: your espresso tastes sour, so you grind finer. And finer. And eventually the shot takes 40 seconds and still tastes sour. What's going on?
Usually it's channeling. When the grind is very fine but the coffee puck wasn't distributed evenly, pressure builds up unevenly. Water finds a channel through the puck and extracts everything there (bitter), while the rest of the puck gets barely 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 doesn't lie in the grind size, but in puck preparation. Distribute the coffee in the portafilter evenly (WDT with a needle works well), then tamp evenly. More on this in our preparation guide. Pre-wetting can also help with channeling because it saturates the puck more evenly before full pressure comes.
If none of that helps and the espresso still tastes sour with the right time and ratio, brew temperature can play a role. Too low a temperature 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 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 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 = more surface area = more extraction per second.
That's why you need a grinder for espresso that can grind fine enough and delivers uniform particle size at the same time. Not every coffee grinder can do that. A decent espresso grinder costs about 200 euros and up. Cheaper grinders can grind fine, but unevenly — with many coarse and many overly fine particles at the same time. This leads to under- and over-extraction in the same shot. Our big espresso grinder test shows which grinders can do it. A curated selection of recommended grinders can be found in the espresso grinder selection. Hand grinders under 100 euros are often the best choice in the budget range.
Setting grind size: Dialing in with five shots
If you have a new grinder or want to start a new coffee, this method gets you to your goal quickly. Define the recipe or use our recipe. We provide a recipe for every espresso in our shop.
Shot 1: Start with a setting that seems roughly right to you. Dose 18 g, pull to 36 g, and time it. If the shot takes under 20 seconds: adjust significantly finer. Over 35 seconds: adjust significantly 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. Make small corrections, taste, evaluate. If the espresso is in the time window and tastes good to you: you're done. If it's in the time window but doesn't taste good: continue reading at espresso too sour or adjust the brew ratio (slightly more or less water).
Yes, that costs you five shots of coffee. Think of it as an investment — afterward you'll know where your grinder stands and only need to make minor adjustments.
More on brew time and why it's your most important diagnostic tool: Espresso extraction time: When does brew time really matter?
Your espresso tastes sour? Then check out our detailed troubleshooting article: Espresso too sour — what to do?
