Espresso Skills & Dialling In
Coffee Grind Size Explained for Espresso: A Barista’s Guide
Espresso running too fast or too slow? Learn how coffee grind size affects extraction, flavour and shot time — and how baristas use the grinder to dial in espresso.
By Carlos – Founder & Head Trainer, I Am Barista
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One of the most important skills a barista can develop is understanding the grinder. You can have great coffee beans and an excellent espresso machine, but if the grind size is wrong, the espresso can still taste unbalanced.
Grind size affects how quickly water moves through the coffee and how the espresso extracts. A small grinder adjustment can change a shot from fast, weak and sour to slow, bitter and over-extracted — or help bring it into balance.
This process is commonly called dialling in espresso. In this guide, we will explain what grind size means, what happens when espresso runs too fast or too slow, and how baristas approach grinder adjustments.
Too Fast?
If espresso flows too quickly, a finer grind can create more resistance and slow the extraction.
Too Slow?
If espresso barely flows or takes too long, a coarser grind can reduce resistance and increase the flow.
Taste Matters
Shot time is useful information, but dialling in ultimately means using extraction data together with flavour.
What Is Coffee Grind Size?
Grind size describes how fine or coarse coffee becomes after passing through a grinder. Imagine the difference between fine sand and small pieces of gravel. Both may start from the same material, but their particle size changes how easily water can move between them.
Espresso normally requires a relatively fine grind because the machine pushes water through the coffee under pressure in a short period of time. The coffee needs to create enough resistance for extraction to occur properly.
The exact grinder setting is not universal. Different grinders, coffees, roast profiles, doses and environmental conditions can require different settings.
Why Does Grind Size Matter for Espresso?
When water passes through ground coffee, it dissolves flavour compounds from the coffee. The grind affects both how easily water can travel through the coffee bed and how much surface area is exposed to the water.
A finer grind generally creates more resistance and slows the shot. A coarser grind generally creates less resistance and allows the espresso to flow faster.
This is why the grinder is one of the main tools baristas use when an espresso is not extracting as expected.
Fine vs Coarse: The Simple Espresso Rule
| Grind | Resistance | Espresso Flow | Typical Adjustment |
|---|---|---|---|
| Finer | More | Slower | Use when the shot is running too fast |
| Coarser | Less | Faster | Use when the shot is running too slowly |
This is a useful starting rule, but professional dialling in goes further. A barista should also consider dose, yield, extraction time, consistency and, most importantly, how the espresso tastes.
What Does “Dialling In” Espresso Mean?
Dialling in is the process of adjusting espresso variables to achieve a desired extraction and flavour. Baristas commonly work with variables including dose, yield, grind size and extraction time.
Rather than simply deciding whether a shot looks good, a barista can weigh the coffee going into the portafilter, measure the espresso coming out and monitor how long the extraction takes.
These numbers create a repeatable starting point. Taste then helps determine whether further adjustment is needed.
Espresso Running Too Fast: Should You Grind Finer?
If an espresso reaches the target yield much faster than expected, the water may be passing through the coffee too easily.
One common adjustment is to make the grind finer. Finer particles generally create more resistance, slowing the flow and changing the extraction.
A fast shot may taste thin, sharp, sour or lacking in sweetness, although flavour should always be evaluated rather than diagnosed from time alone.
Espresso Running Too Slow: Should You Grind Coarser?
If espresso takes much longer than expected to reach the target yield, or barely flows from the portafilter, there may be too much resistance.
Moving the grinder coarser increases particle size and generally allows water to travel through the coffee more easily.
An excessively slow extraction may taste harsh, bitter, dry or unbalanced, but again, time is only one piece of information. Taste is essential.
What Are Dose, Yield and Extraction Time?
Understanding grind size becomes much easier when you understand the basic measurements used during espresso preparation.
Dose is the amount of dry ground coffee placed into the portafilter basket.
Yield is the amount of liquid espresso produced in the cup.
Extraction time is how long it takes to produce that espresso.
Instead of saying, “This espresso looks about right,” a barista can use these measurements to create a recipe and then adjust one variable while observing what happens.
A Simple Espresso Recipe Example
Imagine you are working with a recipe using an 18 g dose and aiming for approximately 36 g of espresso. This represents a 1:2 brew ratio.
If you reach 36 g extremely quickly, you might make the grind finer and test again. If reaching 36 g takes much longer than your intended recipe, you might move the grinder coarser.
The important point is that these numbers are not universal rules for every coffee. They are an example of how baristas create a measurable recipe and make controlled adjustments.
Want to Understand Espresso Beyond the Basics?
Our private Dial-In Espresso training goes deeper into grinder adjustment, espresso recipes, extraction, flavour and the practical decision-making used to dial in coffee.
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A common mistake when learning to dial in is changing everything at once. The grind changes, the dose changes and the yield changes — and suddenly it becomes difficult to understand what actually improved or damaged the espresso.
Controlled adjustment makes troubleshooting easier. Keep the recipe as consistent as possible, change one variable and observe the result.
This approach helps baristas build an understanding of cause and effect rather than simply moving the grinder until the espresso happens to look right.
Why Does Espresso Grind Size Change During the Day?
One of the first surprises for new baristas is discovering that yesterday’s grinder setting — or even this morning’s setting — may not produce exactly the same result later.
Coffee is an agricultural product and espresso preparation is affected by many variables. The coffee itself changes as it ages after roasting, while environmental conditions such as temperature and humidity can also influence how coffee behaves.
This is why professional baristas monitor espresso throughout service instead of assuming that one grinder setting will remain perfect forever.
Does Every Coffee Use the Same Grind Size?
No. There is no universal espresso grind setting.
Different coffees can behave differently depending on the bean, roast development, age, grinder, espresso machine, basket, recipe and other variables.
This is also why copying someone else’s grinder number is usually not very useful. “Setting 4” on one grinder does not necessarily mean anything on another grinder.
Why Does My Espresso Taste Sour?
Sourness can be associated with insufficient extraction, but diagnosing espresso purely from one flavour word can be misleading.
If the espresso is flowing unusually fast and tastes sharp, thin and undeveloped, grinding finer may help increase extraction. However, the complete recipe should be considered before making conclusions.
It is also important to remember that acidity is naturally present in coffee. A bright, fruity acidity is not automatically a defect.
Why Does My Espresso Taste Bitter?
Bitterness and dryness can sometimes appear when an espresso is extracting too much or when the recipe is not suited to the coffee.
If the espresso is flowing extremely slowly and tastes harsh or dry, moving the grind coarser may be one adjustment worth testing.
But just like sourness, bitterness cannot be explained by grind size alone. Roast profile, water, temperature, recipe and the coffee itself can all influence flavour.
Grind Size Is Only One Part of Good Espresso
It is easy for beginners to focus entirely on the grinder, but good espresso requires consistency across the whole preparation process.
- Use a consistent dose.
- Distribute the coffee evenly.
- Tamp consistently.
- Keep the portafilter and equipment clean.
- Measure espresso yield.
- Monitor extraction time.
- Taste the espresso.
- Make controlled adjustments.
When your preparation technique is inconsistent, it becomes difficult to know whether the grinder caused the change or whether another part of the process did.
When Should a Beginner Learn to Dial In Espresso?
Beginners should first understand the foundations: how to use the espresso machine safely, prepare the portafilter, dose, distribute, tamp and recognise a basic espresso recipe.
Once those actions become more consistent, learning to dial in is a natural next step because it moves you from simply making espresso to understanding how to control it.
If your goal is to become a barista in Melbourne, understanding the relationship between the grinder and espresso machine can become an important part of your development as you progress beyond beginner skills.
Learning Espresso Dial-In at I Am Barista
At I Am Barista Coffee School, we teach espresso as a process rather than a collection of numbers to memorise. The goal is to understand what is happening in the cup and why you would make a particular adjustment.
Our private Dial-In Espresso training is designed for people who want to go deeper into espresso extraction, grinder adjustment, recipes and flavour. Because the training is private, the session can focus closely on the student’s technique and understanding.
Developing this skill takes practice, but once you understand the relationship between grind size, dose, yield, time and flavour, espresso becomes much less mysterious.
Espresso Grind Size & Dial-In FAQs
What grind size is best for espresso?
Espresso generally uses a fine grind, but there is no universal setting. The correct grind depends on the coffee, grinder, recipe and equipment, so baristas adjust it according to extraction and flavour.
Should I grind finer if espresso runs too fast?
Generally, yes. Grinding finer creates more resistance and usually slows espresso flow. Keep the rest of the recipe consistent so you can properly evaluate the change.
Should I grind coarser if espresso runs too slowly?
A coarser grind generally reduces resistance and increases flow, so it is a common adjustment when espresso is extracting much more slowly than intended.
What does dialling in espresso mean?
Dialling in means adjusting espresso variables such as grind size, dose and yield to achieve the desired extraction and flavour from a particular coffee.
Why does my espresso grind need adjusting every day?
Coffee changes over time and environmental conditions can affect extraction. Baristas therefore monitor their espresso and make grinder adjustments when needed rather than relying permanently on one setting.
Is espresso extraction time all that matters?
No. Extraction time is useful, but dose, yield, preparation consistency and flavour should also be considered. A shot reaching a target time does not automatically mean the espresso tastes good.
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