While you can use a grind size index system such as sieve analysis or laser diffraction, this can be time-consuming, messy and altogether quite fussy for the first cup of the day.
Ultimately, neither method is currently used meaningfully for coffee brewing, and so virtually everyone in the coffee world, from barista champion to home brewer, is stuck explaining their preferred grind size in terms of vague descriptions like "finer than I normally grind for my Chemex" or "a little coarser than a french press grind." These sorts of comparisons often lead to lots of hand gestures, rage and bitter coffee.
I thought I would try to clear the air with a post that actually shows clear photographs four common grind sizes: fine, medium, coarse, and extra course. Here they are, all laid out:
As a basic brewing principle, the smaller the particle, the faster the brew. This is because as the surface area to volume ratio increases, so does the extraction rate of coffee solids.
1. fine: brews a minute or less
A fine grind has a particle size similar to crystallized salt, and is used for quick extractions such as espresso.
2. medium: brews at least three minutes
A medium grind is a bit coarser than Kosher salt, and is most often used for pour over brew methods such as Chemex and Kalita.
3. coarse: brews three to four minutes
It may look similar to drip, but you'll notice that the average particle size is substantially larger, closer to ground black pepper. This size is better for immersion brews that last a little longer, such as those in a french press or a clever dripper.
4. extra coarse: brews four to five minutes
The coarsest of all, this grind is similar in size to sea salt granules and is used most commonly for coffee tasting in a professional setting.
In the pictures, some particles might look like they are too fine or too coarse for the overall grind size, and that's because they are: coffee grinders produce granules along a roughly normal distribution, which is a fancy way of saying the grind size varies but averages out around a central point, like this:
This is why a burr grinder is helpful in brewing coffee how you like it. A burr grinder pulverizes coffee into a more consistent size and shape, whereas a blade grinder slices coffee into irregular chunks. Which is why its grind range is often compared to dust and boulders.
Why does it all matter? Grind size is one of the most easily controlled variables when brewing coffee. Having a grasp of what you like and understanding how your grind affects that gives you the power to change your brew and know what you'll get.
Simply put, if your coffee is too bitter, your grind is too fine or your brew is too long. If it tastes like hay or hose water, it's too coarse or you've not brewed for long enough!
Looking for recipes using a specific grind size? Here's how to brew an AeroPress espresso
Looking for coffee that will still be delicious if you don't get it perfect on your first try? Bring Kaffeologie home!