These days, most baristas are accustomed to thinking about and controlling the many factors that affect an espresso’s taste. They may have also honed the art of perfectly steaming milk and be pouring beautiful designs on their drinks. Today we’ll be talking about something which is often overlooked: the amount of milk we’re mixing in to that coffee, and how it affects the strength and flavour of the coffee we drink.

The ratio of milk to coffee is such a simple thing to control, it’s amazing that so many people don’t even consider changing it. At home, a barista will often just use whatever mugs they have in the cupboard, while in a café, an owner will often simply buy the cups they like the look of, or whatever is easily available to them. However, the size of the cup will be a key factor in determining the strength and drinking experience of the final coffee. In fact, there’s an argument to be made that it’s the only decision we make that will change the final strength of the coffee. That argument goes like this: for a given espresso machine and basket, there are a small range of viable doses we can use. Although it is possible to change our basket size, this is not common practice. Therefore, with our dose fixed, we will need to make a decision about the brew ratio. Although this decision will affect the strength, it makes much more sense to base the decision on getting the tastiest brew we can. Therefore, we end up with an espresso of fixed strength and size, and the strength of the final beverage will be determined by the milk we mix into it.

So, what size cup should we be using? Firstly, I think we need to set some goals for what we want out of our milk drink. Personally, I want mine to taste primarily “like coffee” and not primarily “like milk.” This will mean different things to different people, but by tasting some different ratios you should be able to find where your goalposts are. The character of the milk we’re using is certainly going to weigh in here: a creamier milk or a milk with a stronger inherent flavour will be more present in the profile — sometimes deliciously and sometimes overwhelming the coffee element. Then we have the amount of foam. As many a barista competitor will know, a foamier cappuccino will taste stronger, as we end up with less milk and more air in the cup. The brew ratio of the espresso is also going to affect things: let’s compare a single espresso with a 22g yield to a longer, 33g shot. The second shot will often have a higher extraction, leading to an increase in strength, but it will also displace a whole 10ml of milk, adding to the perceived strength of the drink. Lastly, we should consider the roast profile of the coffee used. Generally speaking, a darker roast will lead to increased strength perception in the cup. However, at a certain point a darker roast will start to introduce roast defects into the cup, leading to a coffee that may taste a bit stronger, but not in a good way (ashy, burnt, bitter.) At Five Senses, we roast to maximize the development of the particular coffee, without introducing any roast defects. The relationship of cup size to perceived value for money is also not to be discounted, but will have to be up to café owner’s judgment of their target market to determine. However, it’s my experience that for every “bigger = better” customer out there, there is another “smaller = quality” customer just around the corner.

Now, let’s talk numbers. Fair warning: we’re veering into personal opinion territory here. My first piece of advice is: measure the actual volume of your cup, as many cups are as much as 10-15% off their advertised volumes. Now, we’ll need an example espresso: let’s use a single shot of our Crompton Road blend, pulled to our standard recipe. This results in two single shots, 22g in size, pulled at a 1:2 ratio. To me, this coffee tastes delicious in cups in the 150ml-190ml range. At the 150ml range the coffee is punchy and certainly the dominant flavour, while at the 190ml end the coffee is creamier and sweeter, but still definitely in balance with the milk flavour. Going too far outside this range either washes out the coffee with excess milk flavour, or results in a drier, “punch in the mouth” type intensity of flavour.

The 8oz Problem
Café owners at the moment are presented with a unique problem when considering the size of takeaway cups to use. The arbitrary standard cup sizes available historically have been 8oz (235ml), 12oz (355ml), and 16oz (475ml). These sizes are normally referred to as small1, medium and large. In recent years, many specialty cafes have stopped selling the 16oz cup, leaving them with a line-up of 8oz and 12oz. This presents an obvious problem: there’s no way to get the same strength/flavour profile in both cups with our standard single or double shot. Which means we either sell a single shot 8oz that’s weaker than we’d like, giving our customers a sub-optimal experience, or put a double shot in both the 8 and the 12, giving our small customers an extra strong coffee. The additional downside of this approach is that our material and staff costs are very similar between the two drinks, with only a small amount of milk between them. This is an unfortunate situation, but it has an obvious solution: substitute the 8oz cup for the smaller, 6oz (175ml) version. This puts us right in the previously identified sweet zone for our single shot, and lets us achieve a consistent flavour strength across both sizes and a dine in and take away flavour profile. In my experience, changing the strength of your coffee is a really good way to put your customers off, so this consistency across your offerings can be key.

In conclusion, there are many potential benefits to be had from considering the amount of milk you put in your flat white, and the size of cup you’re serving it in. It is an essential factor in the enjoyment of your drinks, and I hope this article spurs you to investigate further. Although I firmly encourage you to make your own mind up about this, I wanted to leave you with some concrete recommendations:

  • Using a shot of approximately 20g size, a cup size of 150ml-200ml will give you an excellent balance of strength and flavour.
  • This translates to using 6oz and 12oz cups for takeaway, with a single shot in the first and a double shot in the second.
  • If you are set on using an 8oz cup, it would make more sense to keep the double/single ratio and pair it with a 16oz cup. By using a larger dose in a bigger basket we can avoid the coffee flavour being lost in the extra milk.

Happy drinking!

1. This means the "small” is far larger than most normal dine-in cups, which is compounded by some “8oz” cups I’ve encountered in the wild hitting actual volumes of up to 280ml.

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