FiXX Coffee grinding into a portafilter for espresso

Unlocking the Secrets of Coffee Grind Size - A Comprehensive Guide

It is easy to think of coffee as magic beans. Endless flavours. The power to bestow vitality! They literally grow on trees! Coffee is a daily staple for a large percentage of the world. It is an easy place to lose oneself with a myriad of different varieties, processes, roast levels and ways to brew. 


But they are not magic beans. In fact, they're technically not beans at all, but that's beside the point. Unlocking those flavours requires a bit of skill and understanding. And one of the most critical elements to understand is grind size. Even if you have the nicest, freshest coffee beans brewed using the most expensive, top-of-the-line brewing equipment, if your grind size isn't right, your coffee won't taste right either. 


Read on to find out more.



What is Coffee Grind Size and Why Does It Matter?

Coffee beans are awesome. I think we can all agree on that. But they're stubborn little feckers that need to be roughed up a bit to give up their flavour (not that I agree with that method of persuasion!). The more surface area you can expose to water, the more flavour you'll extract. If you plonked a handful of coffee beans into a cup of boiling water, you would extract flavour, but obviously, it would not be a good flavour. And so, they need to be ground down to size. 


Grind size refers to the coarseness or fineness of ground coffee. Getting it right is one of the most critical elements when it comes to making a delicious cup of coffee. You're probably already aware that certain coffee brewers require different types of grinds. Espresso is perhaps the most obvious, and the example most people tend to use is that of sand versus pebbles. Allow me to explain. 


When brewing Espresso, you need a finely ground coffee like sand. When the coffee is placed into a portafilter and locked into an Espresso machine, the water is forced through the bed of coffee at pressure. Only a fine grind size, like sand, ensures a consistent, slow flow through the coffee bed to extract all the delicious flavour. If the grind was too coarse, like pebbles, the water would flow too quickly through the coffee to extract all the flavours. This would be known as under-extracted coffee. On the flip side, if the coffee is ground too finely, it would take way too long for the water to pass through the bed of coffee, over-extracting it. 



Signs of Over-Extraction and Under-Extraction in Coffee

Essentially, every time you make a coffee, regardless of what equipment you use, you are trying to extract the perfect amount of flavour from your coffee. Different compounds in coffee dissolve at different rates during the brewing process, and grind size plays a crucial role in controlling the extraction. If your grind size is incorrect, you'll likely end up with an over- or under-extracted coffee. But how can you tell? What are the differences? 


  • Under Extraction:

    This is when you have not extracted enough flavour from your ground coffee. If your coffee tastes sharp, sour, or overly acidic, it could indicate under-extraction. Under-extracted coffee might lack depth and complexity in its flavour profile, resulting in a weak or thin taste. It can occur when your grind size is too coarse.


  • Over Extraction:

    This is when you have extracted too much flavour from your coffee. Over-extracted coffee often tastes excessively bitter, harsh, or astringent. It occurs when too many compounds, including bitter ones, have been extracted from the grounds. Over-extracted coffee can leave a dry, puckering sensation in your mouth due to the excess extraction of tannins, resulting in an unpleasant mouthfeel. Over-extraction is common if your grind size is too fine.


In addition to the grind size, other factors such as brewing time, water temperature, and coffee-to-water ratio can impact your final cup. But that's a conversation for another day. Proper extraction is essential to achieve the best flavours from your coffee grounds without experiencing the negative effects of under or over-extraction.



What Are the Different Grind Size Categories?

The tiniest adjustment to grind size can make a massive difference in flavour profile. Even if, on paper, it's a matter of microns, when this coffee comes into contact with water, the amount of surface that is exposed to the water could be doubled. In Espresso, the difference in a shot that poured in 19 seconds compared to 26 seconds can be very obvious. 


Most brewing methods are more forgiving than Espresso, though. That's why a good barista requires good training (which we do at FiXX, by the way!). But generally, grind size can be broken down into seven broad categories. I'll break down what these are and which brewing method is best suited to each. 


Extra Coarse Grind

This grind setting is only practical for cold-brew coffee. But it's a good starting point for showing how grind size affects brew time. As the name suggests, this method brews coffee using cold water. This means extracting flavour compounds that quickly dissolve in hot water takes much longer (12-24hrs). Because of this extended contact time between the water and the coffee, an extra coarse grind is required to ensure the cold brew doesn't over-extract. 

  • Looks Like: Coarse ground black pepper
  • Suitable For: Cold Brew


Coarse Grind

Immersion brewing is the name given to methods where all the coffee hangs out with all the water before being filtered, e.g., French Press/Cafetiere and Clever Dripper. These methods tend to have a longer brew time, resulting in a full-bodied coffee. This extended brew time requires a coarse grind size.


Medium-Coarse Grind

As we go on, you'll notice the direct correlation between brew time and grind size. This grind size works well for a Chemex. Although the Chemex is a pour-over brewer, which I've suggested a different grind size for below, the flow of water through it is significantly slower than other pour-over brewers because of the Chemex's double-bonded filter papers. As a result, a slightly coarser grind is optimal. This size will also work well for home coffee makers like a Moccamaster.

  • Looks Like: Coarse sand
  • Suitable For: Chemex, home coffee brewers


Medium Grind

This is a bit of a jack-of-all-trades setting. And it is what you can expect from ground FiXX Coffee. It's a good starting point when trying a new coffee, as it should be easy enough to know if you need to go a bit finer or a bit coarser. If you do not have a grinder, though, when you order from us, leave a note as to what type of brewer you have, and we'll grind accordingly. 

  • Looks Like: Granulated sugar
  • Suitable For: Flat-bottomed or cone-shaped pour-over filter brewers, French Press/Cafetiere, home coffee brewers, AeroPress


Medium-Fine Grind

As grind settings get finer, a bit of pressure might be needed to force the water to pass through the bed of coffee. The exception in this list is the Hario V60. This is because its conical shape helps water flow evenly through it, making it able to handle a finer grind quite well. 

  • Looks Like: Sand
  • Suitable For: Stovetop, Moka pot, AeroPress, V60


Fine Grind

This could be called espresso grind as it is best suited for Espresso machines. A stovetop/moka pot can brew on this setting, but they don't generate enough pressure to flow through a bed this fine quickly. This makes it easy to over-extract the coffee. Also, not all grinders can grind this fine. So, if you are in the market, make sure you check first (more on grinders below). 

  • Looks Like: Table Salt
  • Suitable For: Espresso


Extra Fine Grind

Like the extra coarse is to Cold Brew, this grind size only suits one type of brewing method: Turkish coffee. This method involves rapidly boiling very finely ground coffee with water and sometimes sugar in a small copper pot called a cezve or ibriki.

  • Looks Like: Flour
  • Suitable For: Turkish Coffee



Certain brewers can handle different grind sizes better than others. The AeroPress is an excellent example of this. In fact, its ability to brew with varying grind sizes is one of the reasons it is so popular. So, the below coffee grind size chart is only a rough guide. Ultimately, you're the master of your coffee experience. If you've got a good grinder at home, play around and adjust whenever you get a new coffee. Different blends, roast types and processes can have various optimal grind sizes. 



FiXX Coffee grind size chart




Troubleshooting Grind Size Issues

As mentioned earlier, the most common problem you'll likely encounter is over- and under-extraction. If your coffee tastes over-extracted (too strong, bitter), you'll need to grind coarser. Under-extracted (too weak, sour), grind finer. But here are a few other things to consider.


Grind uniformity:

Grind uniformity refers to the consistency of the coffee grounds' particle sizes after grinding and is crucial for an even extraction during brewing. Blade grinders, although cheap and convenient, offer poor uniformity. They work by rapidly spinning one blade that essentially smashes the coffee beans down to size. This violent method of grinding produces many small particles alongside the larger ones. When brewed together, the smaller coffee grinds will brew much quicker, and this can lead to an uneven extraction. You can find tips here on how to help with this issue if you own a blade grinder.


Grinder Quality:

For consistent uniformity, the best option is a burr grinder. These have two adjustable flat or conical plates set a desired distance apart, forcing the whole beans through to be ground to that specific size. Although they are generally adjustable, not all can grind fine enough for brewing Espresso. Needless to say, as you go up in price, you tend to go up in quality. And the higher the quality, the better the grind consistency. 


Roast type: 

How dark or light a coffee is roasted will affect how it grinds. As green coffee beans are exposed to heat, they lose density and become more porous, and this means the darker a roast gets, the more soluble the coffee bean becomes. It's one of the reasons most Espresso blends tend to lean toward darker roasts. But this lack of density also makes darker roast beans more brittle. And if you're grinding coffee with a blade grinder, this can significantly decrease your chances of uniformity. So, depending on what roast level you're brewing with, you might want to adjust your grind size.

  • Light Roast (FiXX Single Origin): Light roasts are less porous than darker ones, so their compounds extract more slowly. Grinding finer with lighter roasts will expose more surface area to the water, helping the extraction.
  • Medium Roast (FiXX Lisbon): As this is a grind for all seasons, you'll need to judge extraction depending on how you're brewing. So you might need to go finer or coarser with this one.
  • Dark Roast (FiXX Cubano): The opposite end of the spectrum to light roasts, so basically, reverse what you do. A coarser grind will reduce the surface area, slowing the extraction.



Being able to tell if your coffee has been extracted perfectly is kind of hard when your coffee is stale to begin with. As coffee grounds are tiny particles compared to whole beans, ground coffee freshness will decay much faster when they're exposed to oxygen, light, heat and moisture. So, where possible, buy whole beans and grind when needed. You can find tips for storing coffee grinds in our blog here. But if you don't have time to read another blog, I'll share this one quick tip. DON'T STORE COFFEE IN YOUR FRIDGE!!



In Conclusion

Basically, it'll all come back to extraction and your preference there of. You are the master of your own brew. But being able to recognise if a coffee is over- or under-extracted and then knowing how to adjust your grind accordingly will go a long way, assuming you own a grinder, of course. And if you don't, that's ok too. Just let FiXX know how you brew your coffee when ordering, and we'll grind it for you.


So, I hope that helps clear up a few things. But as with most things in coffee, more answers give rise to more questions. And nearly all the answers to these questions will be "Yes" with a "...but" or "No" with an "...unless". But what do you expect? They're not magic beans, after all.


Thanks for reading.



  • Kevin Acheson

Kevin has worked in and around the coffee industry for over 20 years in Ireland, the UK, the Netherlands, and Australia.