How Often Should You Recalibrate your Coffee Grinder?

This is a question our customers often ask us in a number of different ways.

"I adjusted my grinder but the coffee is coming out too fast/slow again, what should I do?"

"I dialled in my coffee on Monday, why is it out again?"

"How do I know when I need to change my grind size?"

These are all different variations on the same theme. Let me explain:

Espresso Extraction Time Depends on Grind Size

If your coffee roaster has provided you with a target recipe for your espresso, it might look something like this:

18 grams of coffee to 36 grams of espresso in 26-28 seconds.

What this essentially means is that you need 18 grams of ground coffee in your portafilter, and you need to brew 36 grams of espresso into the cup (using a scale to measure). That process should take 26 to 28 seconds for the best tasting espresso.

The way you achieve that target extraction time is by adjusting the grind size of your coffee particles by tweaking the grind setting on your espresso grinder. 

If your coffee is extracting too quickly (less than 26 seconds), you need to grind finer. This adds greater resistance inside the coffee puck, making it more difficult for the water to pass through. 

On the other hand, if the coffee extracts too slowly, there is too much resistance building inside the puck and you need to grind coarser in order to reduce resistance and speed up the shot.

So, When Should I Adjust My Grinder?

The simple answer is... whenever you notice that your coffee is not extracting within the correct extraction time. 

So, if your recipe suggests a 26-28 second extraction time, you might want to adjust your grinder slightly if you're noticing a 20 or 30 second brew time (grinding finer if 20, coarser if 30).

How much you allow your extract time to vary really depends on how busy you are and how realistic it is for your baristas to constantly be mindful of extraction times. A 24 or 25 second extraction will probably taste fine, so you can probably let it fly.

However, your baristas  should take note of large differences in extraction times and adjust your grinder whenever possible to achieve the correct recipe.

When to Grind Finer

As mentioned, you should grind finer whenever your espresso is running too fast.

Make sure your coffee dose and espresso output stay the same, and grind slightly finer to slow down your shot time.

When to Grind Coarser

Similarly, you should grind coarser whenever your espresso is running too slowly. If you’re consistently seeing shot times well above your target range – for example, 32–35 seconds instead of 26–28 – it usually means there’s too much resistance inside the puck.

Keep your coffee dose and espresso output the same, and make a small adjustment towards a coarser grind to speed the flow back up.

A good rule of thumb is to make small, incremental adjustments rather than big jumps. A minor tweak is often all you need to bring the extraction back on track, and you'll develop a sense of how large of a jump you should make over time.

How Often Should You (Realistically) Adjust Your Coffee Grinder?

In an ideal world, baristas should tweak their grinder as often as needed throughout the day to keep every espresso pouring within the recipe - like keeping your hands on the steering wheel when driving on straight roads.

Coffee is a natural product, and its behaviour changes constantly based on temperature, humidity, age, and how busy your machine has been. Even a shift in the café’s atmosphere or a fresh bag of beans can nudge your extraction time out of range.

But the reality is very different in most cafés. When the queue is out the door, grinders are the last thing on your team’s mind. Not every member of staff will be trained or confident enough to adjust the grind, and even those who are may not have the time to stop, pull a test shot and make a correction.

So instead of aiming for perfection, aim for reasonable consistency. Encourage your baristas to:

• Dial in the coffee first thing in the morning
• Keep an eye on extraction times during quieter moments
• Correct large swings whenever possible
• Taste the coffee regularly to familiarise yourself with the impact of extraction times

This approach strikes the right balance between quality and practicality. Over time, your team will get better at spotting patterns and knowing when an adjustment really matters.

Check out our quick introduction video below for a brief explainer.