Getting the grind size wrong is one of the common mistakes even the most advanced coffee lovers make. Your coffee grind size determines the extraction time, which means it can affect the taste of your Espresso.

The Basics

Why is your grind size so important? Well, it affects the amount of coffee ground, the flow rate, extraction time, and therefore the over-all flavour of your coffee. Grind size is one of the most crucial parts of a successful coffee, because it allows you to compensate for elements that are more difficult to control such as the weather, or the freshness of your coffee beans.

The finer the grind of your coffee beans, the faster your coffee will extract. This is because there is more surface area for the coffee grounds is exposed to water. A coarser grind therefore results in a slower extraction time.

The extraction time is important because if your coffee is under extracted your espresso will be weak and lacking in flavour, over extracted and it will become bitter. (Contrary to popular belief, coffee is not supposed to have a super bitter aftertaste!)

Choosing grind size 

Now you know why it’s important to get the grind size correct, but how exactly do you get it right? Here are some of the things that will help you choose the right size.

Type of roast

Understanding your bean profile is the most important factor in choosing your grind size.

We have 4 profiles: light, medium, medium to dark and dark roast.

Usually, finer grinds work better for the less porous lighter roast, and dark roasts need coarser grinds. This is because darker roasts are more bitter naturally, so a shorter extraction time prevents over-extraction of those bitter flavours. Adjust the grind size depending on the level of your roast, finer for lighter roast.

Brewing Method

It’s also important to keep your grind size close to the ideal size for your chosen brewing device.

Pressurised brewing methods such as an espresso machine involve a very short amount of contact time between the coffee and water, so a fine grind is used to prevent under extraction. This means even if you’re using a dark roast in your espresso machine, your grind should still be relatively fine, just a bit coarser than your lighter roast espresso.

Immersion brewing methods such as cold brew or a French press involve a much longer contact time between coffee grounds and water, so a coarser grind is typically used to prevent over extraction of bitter flavours.

Pour over or drip methods fall somewhere in the middle, therefore you should use a medium grind size.

Weather and Temperature

Weather and temperature are also very important factors in choosing your grind size. In cold weather, the coffee will extract more slowly so you should make the grind coarser to compensate. Hot weather has two variables: in hot and dry weather the coffee will naturally extract more quickly, so you should make the grind finer to slow it down, however if the weather is humid, the opposite is true ­– the coffee will extract more slowly as it has already absorbed some moisture from the air, so you should make the grind coarser again.

To simplify:

Cold weather/humid weather = coarser grind

Hot and dry weather = finer grind

These adjustments are not just seasonal, but often need to be made throughout the day as the temperature fluctuates from morning to afternoon. So make sure you keep an eye on the weather and calibrate the grinder for consistency across the day.

Types of grinder

The type of grinder you use will also affect the grind.

It starts with the type of the grinder. If you happen to buy one of those supermarket grinders, you will get a mixture of even and uneven grind. It is advisable to get a burr grinder either conical or flat for consistency and even grind.

Blade grinders use a blade to shop up the beans to a fine consistency. Quiter than other grinders and easy to use, they are a popular choice for beginners.

Burr grinders use two metal burrs which grind the coffee between them, burr grinders create a much more consistent grind that blade grinders, and are the standard for professional baristas.

How to adjust your grinder

This may vary depending on the type of grinder and type of coffee, but the principle remains the same.

Adjust your burr to get your grind size. To the left you will get a coarser grind and to the right, a finer grind.

Once your coffee is ground, brew it up and see how it tastes! If using an espresso machine, take note of the extraction time (optimal is between 25-30 seconds). You can then further adjust your grind size based on the extraction time and flavour you’ve ended up with.

Finally, don’t worry if this all sounds complicated! We have years of experience! Just experiment with different grind sizes and you will soon learn what works for your set-up and tastes. And if you want an expert to guide you through be sure to sign up for our 5 day Professional Barista Course where we can help you learn all you need to know about the basics of making a great cup of coffee.