One of the most satisfying yet frustrating aspects of home brewing is seeking to master the art of grinding. I have often thought that one of the quintessential joys of coffee is that moment when you walk into your favourite cafe and are hit by the aroma of freshly roasted and freshly ground beans. And the amazing thing is that you can, at least in part, replicate that experience in your own kitchen!
We have sought to make this article a comprehensive guide to home coffee grinding. We will cover everything from grind size for different brewing methods, to different types of grinders, to the technical relationship between grinding and extraction. So whether you are new to the game or just getting some tips and reminders we hope you find it helpful.
Why should you Grind your own Coffee?
So is it worth the hassle? There are an abundance of speciality roasters that now offer pre-ground beans delivered straight to your doorstep, so is it worth taking the leap and grinding from home? Well the fact that you are reading this article is definitely a step in the right direction and possibly an indicator that you are at least considering it. And we think that the answer is absolutely. There are basically two massive advantages of grinding your own beans; fresher coffee and the freedom to experiment.
> Fresher Coffee
As some of you may know coffee beans are technically fresh produce and as such always fall somewhere on the spectrum between fresh and flavoursome and stale and generic. The general rule of thumb is that whole coffee beans are best consumed in the first 30 days after they are roasted. After this the flavour and aroma will become more and more generic and lose much of the flavour profile that is specific to it. Old coffee = bad coffee.
Why this matters for grinding is that as soon as whole beans are ground the process of going stale is accelerated rapidly. As soon as a coffee bean is broken up and exposed to the air it begins to release aromatics and quickens the process of oxidation which decreases the flavour and enjoyableness of the final coffee. This is the single strongest argument for investing in a burr grinder if you don’t already have one. It means that, provided your beans are fresh, they will retain the maximum flavour and aroma for your cup of brew! We recommend that coffee beans should be used within 3-5 minutes of being ground.
> The Freedom to Experiment
Another significant advantage to grinding your own beans is that you are given the ability to experiment and find the perfect grind size for your palate and your brewing method. This is actually not just a nice incentive but really important for good coffee. As we will show below each brewing method (Aeropress, French Press, Pour over, Espresso etc) has a different optimal grind size. If you buy pre-ground coffee, especially mass produced, you run the risk of getting the wrong grind size for your specific method which will in turn sabotage the flavour of your coffee. If you do go pre-ground we recommend buying whole bean and then taking it to a local specialty cafe and asking them to grind it for you for say Aeropress. Grinding at home means you have the freedom not just to find the perfect grind size for your brew method but to even switch between brewing methods.
Grinding your own beans also means that you have the ability to really experiment with your coffee brewing. It means that you can try a slightly coarser grind for V60, or a very fine grind for Aeropress and give it a shot to see how it tastes. For this reason a quality burr grinder is really a non-negotiable if you are serious about getting into coffee. While you can make great coffee without one, it will restrict your ability to really grow and develop in the world of coffee.
Finally, we can say from experience that it is actually just an incredibly fun and satisfying way to up your coffee game. We own both an espresso and a hand grinder and it is surprising how satisfying it is to start your morning with the smell of freshly ground beans and a cup of brew your own hands have ground! A bit weird but if you grind your own beans then I am sure you know what I am talking about.
Grind Guide for Different Brewing Methods
The biggest struggle with grinding your own beans is that there is no universal number or measurement that is able to communicate specific grind size. What this means is that every grinder has different marks and numbers to communicate different grind sizes. So where the number 10 on one given grinder may indicate a very fine grind, on another grinder 10 may be quite coarse or at least won’t be the exact same size. In addition, even two models of the exact same coffee grinder may be different depending on the age of the grinder and the wear on the burrs. So to remedy this the coffee industry has opted for generic size of fine, medium, and coarse with any number of different subcategories between them.
Sadly we can’t tell you that for your grinder you need to set it on 7 for pour over. Instead we can only give you a rough indication of what the grind for a given brewing method ought to look like. From there it will be a process of trying to get your grind to the general ballpark size and then using both taste and often time to hone it in to the perfect size. For example, for pour over you will often be aiming to have a brew time of 2.5-3 minutes and so if you find it is taking longer then you need to make the grind setting coarser or if it is too quick then the grind size needs to be finer. Similarly, for French Press how much pressure is needed to push down the plunger is a good indicator of if the grind setting is right.
However, taste is the most important factor. Keep tweaking the grind size until you think it tastes the best. That is what it is really all about.
Below are photos of what the different broad grind sizes look like and which brewing methods we recommend for each.
This is the finest grind setting and it is worth noting that most grinders struggle to grind this fine. The grind should resemble flour and clump together. This is the grind size that is used for Espresso and Turkish (although Turkish actually requires it to be even finer than is required for espresso).
This is slightly coarser than the extra fine setting but still relatively fine. It should be slightly finer than table salt. It is the grind setting for Moka Pot/Stovetop, V60, and Aeropress (with a quick brew time).
This is what most pre-ground coffee, that is not specifically espresso, comes in. It should have a consistency similar to sand. It is the grind setting for drip machines or Aeropress (with a longer steeping time).
At this size the particles are starting to look like specific little chunks of coffee bean. It should resemble rough sand. This is the grind setting for Kalita Wave and Chemex.
This is the coarsest size and is used for brewing methods with the longest contact time between the beans and water. It should resemble sea salt. This is the grind setting for French Press and Cold Brew.
Types of Coffee Grinders
There are basically three categories of burr grinders that it is helpful to be familiar with. Blade grinders are not one of the categories because ultimately their lack of consistency makes them not worth using. Because grind size and uniformity are so important for coffee, it is probably better to opt for pre-ground than to use a blade grinder or super cheap burr grinder.
These tend to be very compact grinders which obviously don’t use electricity but instead require you to grind by hand usually by rotating a handle. The real advantage of hand grinders is that they are far cheaper than automatic grinders and you get a lot more for your money. For the price of a quality entry level automatic grinder you can usually get a premium hand grinder with high quality burrs and pretty amazing grind consistency. Also hand grinders obviously tend to be more portable, and a decent quality one will last for ages. The downside of course is that they take both time and effort to grind beans (especially for the fineness required for espresso!) and often are not well suited to grinding large amounts of beans. You can see our article here for more info on hand grinders.
Automatic grinders, in contrast, tend to be far bigger, require far less effort, and are better suited to grinding large amounts of beans. Really, the best argument for using an automatic grinder is that it is easy and quick. It usually requires nothing more than a push of a button and takes 10-20s. This is a fairly significant advantage if you are wanting to incorporate grinding into your morning coffee routine and are pushed for time. Automatic grinders do tend to be more expensive than hand grinders and come in both stepped (in which there is a set amount of different grind settings) and stepless models (in which there are almost unlimited possible minor adjustments possible). You can see our guide here for our favourite automatic burr grinders.
These are really a subset of automatic grinders and refers to grinders that are able to grind for espresso. Basically an espresso grinder is one which can make the incredibly fine grind size adjustments that are required for espresso. Espresso grinders tend to use flat plate burrs and be of a very high quality and grind size consistency. This is because, of all the brewing methods, espresso requires the greatest precision. As a result a decent espresso grinder especially for a quality espresso machine tends to be fairly pricey.
Advanced Tips for Coffee Grinding
Accurately Measuring Beans
As a general rule you should always use an accurate scale to measure the weight of the beans that you are grinding. This is far more accurate than ‘eyeballing’ it and will allow you to more easily replicate a coffee that was particularly enjoyable. It is also worth noting that grinders will typically retain some of the ground beans on the burrs so the weight of beans in may not be exactly the same as the ground coffee out. This is especially important for espresso.
Purging an Automatic Grinder
Automatic grinders differ from hand grinders in that the beans typically sit in a hopper rather than putting in the specific amount of beans you want ground. When using an automatic grinder it is important to ‘purge’ the grinder every time you adjust the grind setting. This is done by letting the grinder run for a few seconds and then throwing out the grinds that come out. This is rather painful and can be pricey but the rationale is that if you don’t purge then the grounds that come out will be a mix of the old and new grind sizes and so won’t allow you to see whether you have the right setting. Again this is particularly important for espresso.
Dialing in Espresso
This is really worthy of an entire article which we will hopefully one day write. Here we just wanted to introduce the language and concepts here. Basically ‘dialing in’ a grinder is the process of figuring out the correct grind size for a specific espresso recipe. So a typical espresso recipe would be something like 18 grams of coffee in, 36 grams out, in 26-30s. This becomes the goal which you are seeking to reach on your espresso machine by tweaking the grind size until you are able to get 36 grams of coffee out in 26-30s. This is a real art that does take time to master and really does require an espresso grinder.
The freshness of the coffee beans you are grinding will also affect the grind setting that you use. So you will find that the grind setting which seemed perfect for a batch of beans a few weeks ago is now either under-or over-extracting your brew. This is especially true of espresso which is the most precise brewing method. As such you may find you need to tweak your grind setting as the beans age.
Dark roasted coffee beans tend to be more brittle and more soluble than lighter roasts as they have been exposed to heat for longer. As a result, darker roasts should be grinded slightly coarser than lighter roasts for a given brewing style. Similarly, even the altitude at which a bean is grown may impact the required grind setting. You will generally find that whenever you get a new batch of beans and especially a different blend or type of bean, that you will need to tweak your grind sizes.
Getting Technical: Grinding and Extraction Theory
I am now going to unashamedly go into coffee geek mode and get into some of the nuts and bolts of coffee theory. So if this doesn’t interest you then feel free to skip this section. Otherwise strap in for the ride!
The basic purpose of grinding coffee beans is to facilitate the extraction process by exposing more surface area to the hot water. Basically, the process of making coffee happens as roasted coffee beans are brought into contact with hot water that ‘extracts’ the flavour, ideally resulting in a delicious cup of brew. The problem however, is that this process of extraction is not as straightforward as it sounds and easily extracts either too much or too little from the bean.
A coffee bean is made up of a combination of 30% soluble (can dissolve in hot water) and 70% insoluble (can’t dissolve) compounds. The final flavour of your coffee is largely governed by how much of the 30% soluble part is extracted in your brewing process.
TDS and Extraction Percentages
You have probably heard the terms over and under-extracted tossed around in coffee circles, but these terms are often misunderstood. Instead of referring primarily to the taste of a given coffee they are a way of designating if too much or too little of the beans have been extracted into the final coffee, which will in turn shape the flavour. The general rule of thumb in the specialty coffee industry is that the ideal extraction extracts 18-22% of the coffee bean (or in the case of well known coffee commentator Scott Rao 19-20%). Hence, if a given coffee extracts less than around 15% it is considered under-extracted and will taste sour or overly acidic. Likewise, if it extracts more than 25% it is considered over-extracted and will have a bitter taste.
This extraction process is often related to what is called TDS (the percentage of total dissolved solids ). Your average coffee is typically around 98-99% water with the remaining 1-2% dissolved coffee. This percentage of the dissolved coffee beans is what TDS measures and effectively equals the brew strength of the coffee. TDS is measured using a fancy and expensive device called a refractometer.
After extensive testing the coffee industry has generally agreed that the optimal TDS is 1.15% – 1.35%. This matters for coffee theory as it means that it becomes possible to derive specific coffee recipes that fall in the optimal TDS range as well as extracting the optimal 18-22%. It also actually matters for home brewing as if your coffee tastes off then it is likely because TDS is off or you have either extracted too much or too little from the beans.
This relates to grinding because grind size is one of the major parameters that shapes how much coffee is extracted from the beans. Basically the finer the coffee is ground the slower the water passes through the grinds and the more is extracted from the beans. Similarly, the coarser the coffee is ground the quicker the water passes through the beans and the less coffee is extracted. It is a little bit like if you pour water over a bucket of rocks the water will quickly pass through the rocks to the bottom of the bucket. But if you filled the bucket with sand the water would take a lot longer to reach the bottom of the bucket. Coffee extraction is exactly the same.
Extraction Theory and Coffee Grinding
There are two important implications of extraction theory for brewing. Firstly, it means that the general rule of thumb is that the longer the water will remain in contact with the beans the coarser the ground that is required. So immersion methods like French Press and Cold Brew, in which the coffee is immersed in hot water for a long period of time, require a very coarse grind or else they will over extract and taste bitter and unpleasant. Similarly, infusion methods, in which the water is poured or forced through the grinds, require a finer grind or else they will under-extract and taste sour and unpleasant. This is the reason that espresso requires a very fine grind; because it has an incredibly short contact time between the beans and water of 25-30 seconds This means that if your coffee is tasting bitter and over-extracted or sour and under-extracted then grind size is a vital parameter that may be off.
The other implication of this is that it highlights the vital importance of particle size uniformity. If you are using a cheap blade grinder then chances are that you can even see a mixture of smaller and larger particles among your grinds. The problem with this is that the very small particles (generally called fines) will over-extract while the larger particles (called boulders) will under-extract. Either one of these can and will negatively impact the final flavour of your coffee. That is why if you have a cheap blade grinder then actually coffee pre-ground on a commercial grinder may make a nicer coffee.
This video by Chris Baca makes a similar case that while home grinding is the ideal, pre-ground is better than home grinding with a cheap grinder.
It is also worth noting that there is no such thing as a complete particle size uniformity. Because each bean is a slightly different shape the grinding process will never be completely uniform. Instead the aim is to have the smallest possible particle size distribution. This can be a tricky thing to navigate as a home brewer because there is always going to be a better grinder you can get which will lead to a greater uniformity in grinds. It basically comes down to what your budget is and how far you want to take your hobby/passion/lifestyle of coffee brewing. As shown above it will also depend on whether you opt for a manual or automatic grinder and which brewing method you are grinding for.
To get what is generally called a premium grinder you will be looking at a minimum of about $150 for a hand grinder, similarly for an automatic grinder for manual brewing, and easily $400-$500 for an espresso grinder.
Summing it Up
To sum it up the flavour of coffee is largely governed by how much of the soluble part of a coffee bean is extracted (ideally 18-22%) and how much dissolved coffee ends up in your brew (ideally 1.15-1.35 TDS). Coarse grinds extract slowly and are better for immersion brewing methods while finer grinds extract quickly and are better for infusion brewing methods. While all grinders will produce a range of particle sizes the aim is to have the smallest possible particle size distribution. If you made it this far then well done! You now understand at least one element of coffee theory.
We hope this article has convinced you that the world of grinding is a world worth entering and helped you to do it a little bit better. Feel free to print off the chart of the different grind sizes if you find it helpful.
While grinding can be daunting and difficult it is also immensely rewarding and can really up the quality and enjoyment of your morning brew. As always we would love to hear any questions or comments you have below!