Throughout my years working in coffee, from a full-time cafe barista, to a trainer and competitor, a question I am often asked is “What is the right dose for espresso?”

It is an important and interesting question, and there is no one answer. Your dose when extracting espresso will depend on a number of factors, including the size of basket, how soluble the coffee is you are working with and also the style and structure of flavour you are interested in extracting.

Let’s begin with basket size. Most basket manufacturers will give a gram suggestion, for example 20g baskets are deigned for around 20g of dose. This doesn’t mean basket sizes have to be perfectly aligned with their stated dose, rather they are a guideline and starting point. A key consideration here is how much headspace will there be above the coffee bed when the handle is plugged into the machine.

The reason this is important to understand is because when water hits the puck during espresso extraction, gases from roasting are released and the puck will expand. The more the coffee expands the more space for agitation and movement. With too much space for expansion it can become easier for the water to break the pucks resistance leading to channelling and inconsistency especially in the later stages of extraction.

In competition, 20g VST baskets are the standard – however, when I competed last year at the World Barista Championships in Seoul, I dosed 16.5g in the basket for my espresso coffee. A key reason I didn’t go lower than this dose was because I started experiencing inconsistencies in extraction and flavour below 15g. The only way I could gain any consistency at these low doses was running very fast flow rates.

As I increased my dose, I found that a 16-16.5g dose was where extractions started to become more consistent and flavour profiles didn’t vary as much shot to shot. I have been taught before not to dose too little coffee into a basket but had never actually experienced the change in consistency of extractions. Some of the measures used for this consistency included shot times for the set recipe, extraction yield, giving the coffees a score based on the WBC scoresheet, and also watching the consistency of flow. Lower than 16g shots started to vary more in flavour, the way the shots looked, and also run times suggesting I needed a smaller basket to explore lower doses more effectively.

After extraction, consistency and basket size the next consideration is flavour style and structure. I chose to use less coffee in the basket because I wanted to represent the delicate, elegant structure of this farm and in turn open up its flavour profile with more transparency. High doses generally lead to heavier and more concentrated espresso, which can be great too but there is always a choice baristas have to make between seeking texture and weight or transparency of flavour.

Depending on the desired roast and beverage style a range of doses can be appropriate. For my espresso course in my WBC routine, I was using a very light roast degree to preserve the floral and delicate flavours from the coffee varietal. In an overly generalised sense, roasting a coffee for less time will break down the coffee less, making it harder for water to find and extract from the pores of the coffee surface. Therefore to properly extract the flavour from this roast profile, I needed to use dose as a means of increasing extraction.

Reducing the dose and having less coffee to dissolve from can make a significant affect on how much we develop the flavour in the coffee. This way I was able to use this less roasted coffee and extract very silky espresso with transparent and very unique expression of my coffees floral traits. With this same roast profile at a higher dose, I would not extract enough from the coffee and in turn miss out on sweetness and developed flavour profile.

It is important to understand this method will not work for all roast profiles. For instance, the coffee which I used in Seoul for my milk course was roasted over a longer time period and was broken down more, therefore it was more soluble and easily extractable at 21g dose.

The reason I worked at such a high dose for milk was because I wanted concentration and intensity that I could eventually dilute through milk. This style of espresso drunk on its own can be too heavy and concentrated and intense for many palates with high viscosity overpowering the flavour profile. So with each course I made a choice on whether I wanted to favour complex delicate flavour or more textural elements of the coffee.

So, how do you find the ideal dose for your coffee? The first place to look is at recipe cards or ask the baristas what dose they use where you bought your coffee. Usually there will be a recommended range to work within e.g. milk based 20-21.5g and espresso 18-20g dose. From there, I would start with a 50% brew ratio (18g in 36g out) in around 20-25secs and I will extend the beverage weight if the quality of acid is low.

Once I find roughly where the coffee wants to be ratio wise, I will then make a decision on body and concentration and here, dosing will come into play. Making a big change will help you understand what dose is contributing to the equation but when changing dose make sure to keep the ratio between dose and beverage weight constant (e.g. 20g in 40g out becomes 21g in 42g out).

Making a whole 1g increase in dose will make a significant increase in weight and texture of the coffee. By making a big change here, we know very clearly if this is the right direction or not. If there is too much coffee in the basket, the flavour will become too heavy and sweetness can drop because the amount of coffee is too much for the water to efficiently get to and extract.

Alternatively, if there is too little coffee in the basket then this 1g increase in dose will make your coffee taste significantly more textural, rounded and smooth in its flavour profile. Think of body as filling the gaps between acidity, sweetness and bitterness on your palate. Tasting coffees of different doses side by side can help you make a decision on which is the right direction to go. At the right dose coffees should be more forgiving and have a wider window of where they taste acceptable.

By increasing dose by a whole gram we can see a drastic change in quality, if the change is far better than before you can keep working in that direction using smaller increments 0.5g change at a time until you have found the right dose to work at. Remember we are using dose to find the ballpark, then the other variables of time and exact beverage weight are to fine tune at the end.

It is important to remember that no one dose is perfect for one coffee; as a coffee ages and changes, so too must your approach to it. We must also consider what kind of experience our customers are looking for – will this heavy and textural espresso that I using through milk appease the customers who are looking for that full-bodied experience, or will a lighter expression help you to educate them on the complexities of coffee profiles?

Thanks for reading, and happy dosing!

Hugh Kelly