Grind size is the variable that influences your espresso the most — more than brew temperature, more than tamping pressure, more than the machine. Still, "how fine should I grind?" is a question that has no universal answer. We explain why that's the case, how you can find your grind size, and what you can do if it doesn't taste right. (You'll find the basics of espresso preparation in our brewing guide.)
Why There's No Magic Number
"Set your grinder to 12" is a sentence you read constantly in forums. The problem: setting 12 on your grinder produces a completely different particle size than setting 12 on an identical grinder. Even two identical grinders from the same factory can produce different coarseness at the same setting. The burrs sit slightly differently, calibration varies, and use has worn the burrs differently.
Grind size is therefore not a number 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 Time
You need three things: a scale, a stopwatch (or a scale with a timer), and a recipe as a starting point. Let's take the standard recipe: 18 g of coffee, 36 g espresso in the cup, time window 25–30 seconds.
Dose 18 g of 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 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), your grind size is too fine. The water barely flows 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 that have fine adjustments (e.g., the Eureka Mignon or Niche Zero), it's even just one or two click stops or marks.
The rule of thumb: adjust your grind size in small steps and pull a shot after each change. Don't jump from "way too coarse" directly to "extremely fine" — you'll almost always overshoot, and especially when you go significantly finer, the grinder can even clog. A good rhythm: a small adjustment, one pull, taste, correct. After three or 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 powder from the previous grind setting in the burr chamber. If that gets into your portafilter, it skews your results. We call this leftover coffee dead space, and it varies in size from grinder to grinder.
When You Need to Readjust Grind Size
Grind size isn't a set-and-forget setting. Several factors change how your coffee behaves at the same grind size:
New coffee: Every coffee has different density, cell structure, and roast. When you open a new bag — even of the same coffee — the grind size might be slightly off. With a completely different coffee (e.g., from light to dark roast), you often need to adjust several settings.
Coffee age: Freshly roasted coffee releases CO₂. In the first few days after roasting, it resists water more strongly, and the shot runs slower. At the same time, it bubbles and isn't delicious yet. We recommend waiting about two weeks after roasting before brewing espresso from a coffee. The longer the coffee sits, the finer you'll need to grind it over time.
Humidity: At high humidity, ground coffee swells slightly 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 fixes 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 channeling. When the grind size is very fine, but the coffee puck wasn't evenly distributed, pressure builds unevenly. 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 isn't in the grind size then, but in puck preparation. Distribute coffee in the portafilter evenly (WDT using a needle works well), then tamp evenly. More on this in our brewing 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 your espresso still tastes sour at the right time and ratio, brew temperature might play a role. Too-low temperature extracts fewer acid-binding compounds. Two to three degrees higher 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 demands the finest grind size of all brewing methods. For comparison: Filterkaffee is ground about like fine sand, French press like coarse sea salt. Espresso falls somewhere between powdered sugar and fine sand — much finer than anything else.
There's a simple reason: contact time with 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 must be as large as possible. Finer grind size = more surface area = more extraction per second.
That's why you need a grinder for espresso that can grind fine enough while delivering a uniform particle size. 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 too-fine particles at the same time. This leads to under- and over-extraction in the same shot. Our large espresso grinder test shows which grinders can do it. You'll find a curated selection of recommended grinders in the espresso grinder selection. Hand grinders under 100 euros are often the best choice in the budget range.
Setting Grind Size: Reaching Your Goal in Five Shots
If you have a new grinder or want to open a new coffee, this method gets you to your goal quickly. Define your recipe or use ours. 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: go significantly finer. Over 35 seconds: go significantly coarser.
Shots 2–3: Correct in the right direction, each time in small steps. You should now land in the 22–32 second range.
Shots 4–5: Fine-tuning. Small corrections, taste, evaluate. 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 right: read more at Espresso too sour or adjust your brewing ratio (slightly more or less water).
Yes, that costs you five shots of coffee. Think of it as an investment — after that, 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 the Brew Time Really Start?
Your espresso tastes sour? Then check out our detailed troubleshooting article: Espresso Too Sour — What to Do?
