Calculating Brew Ratios

Over the past few months we have covered many steps on preparing our coffee bed for a great extraction. Yet, how do we know how much coffee we should get in our cup? It's all about brew ratios, that's why you see many baristas and home enthusiasts using scales when they pull a shot.

Before diving into how to determine ratios, what is the best ratio and how to measure them, we must first understand a few terms that are used by the coffee industry as well as what and why we use brew ratios.

Just like most parts of making coffee, consistency is important. How we get consistency is through measuring and controlling our variables. Without this, we would find it very hard to recreate that perfect shot you have dialed in.

Brew ratios are how we control how much coffee we put in the basket, in relation to how much coffee we get in the cup.

The terms used for both our input and output are:

Dose: How much ground coffee you put in the basket. (input)
Yield: How much wet coffee is extracted into the cup. (output)

These two terms plus another term “contact time” are the three basic parts to any espresso recipe you may see communicated by a barista and/or roaster. The dose and yield will give you your brew ratio and the contact time helps you determine the grind size to achieve the recipe.

You may hear people say I settled on a recipe 17g/51sec/34g this represents dose/time/yield. The brew ratio for this recipe is 17:34 or 1:2 (34/17=2). Meaning for every gram of coffee we dose we want 2 grams of yield in the cup.

How to decide on your brew ratio?

With a deeper understanding of brew ratios, the question usually follows, “what is the perfect brew ratio?” Simply put, there is no perfect ratio. Like many parts of coffee, it is a moving target, one we determine by tasting our coffee when dialing in.

That’s not to say it’s scary or hard to give it a go. The standard starting point for espresso brew ratios is 1:2, like in the example above. If no ratio has been advised by a roaster or barista, this is the best place to start.

A 1:2 ratio will almost always taste good and get you in the ballpark. For newcomers to brew ratios, it will often taste good and they will be happy staying with this ratio. As experience grows and your understanding of extraction increases, you can start bringing the ratio down slightly to increase concentration 1:1.8 for example or increase the ratio to 1:2.5 to open up the coffee more and reduce concentration.

We will touch on this subject and the effects of extraction and brew ratios in a later topic, “Advanced Espresso Extraction”. Keep an eye out for this after we cover all the basics.

Setting the brew ratio for your BRUA.

Often when buying coffee from a roaster or cafe, they will give you a brew ratio or a recipe to follow. Sometimes they may tell you the recipe they are using as a guide, like 20g/32sec/42g, which will be based around commercial equipment. This recipe will not work in home equipment like the BRUA, the basket simply can't hold that much coffee and therefore you will not be able to pull a coffee with the given parameters.

Not to worry, with some simple math we can work out the brew ratio and adjust it to fit your BRUA. Firstly we can ignore the time, as this will change dramatically with a different brew ratio and is also affected by different grinders, temperature and other variables. We concentrate on the dose and yield, using the formula Yield/Dose=Brew Ratio or Y/D=BR.

Using the above recipe as an example, Yield=42g and Dose=20g, 42/20=2.1 giving you a brew ratio of 1:2.1, or  for every gram of coffee dosed we need 2.1g of yield.

Often roasters websites or information cards that come with coffee will simply have a ratio like 1:2.1 with them, meaning you can skip the above work and get down to business.

Applying the ratio to work out your dose is very simple. We must first know our basket capacity, The BRUA’s basket is designed for holding approximately 16-18g of coffee. So if we want to sit comfortably in the middle of this and dose 17g of coffee, we use the following formula to determine our target yield D*BR=Y. Using the above BR 2.1 and a dose of 17g will look like  17*2.1=35.7. This now tells us when we dose 17g of coffee into our basket, we will be looking to pull 35.7g of yield in the cup. We measure this accurately by taring our cup on a set of scales and extracting the coffee into the cup while reading the scales to achieve our target yield.

One last ratio that is worth mentioning, you may enjoy experimenting with is a ristretto ratio. Ristrettos usually run a ratio of 1:1 up to 1:1.3 and with the right coffee they can be intense, syrupy and delicious. They can also be acidic and salty, I tend to mainly use them for milk drinks, yet some coffee lovers live for a ristretto, it's all about what works for you. 

Conclusion

Like with all parts of this coffee journey, to understand the effects of different brew ratios properly, it must be put into practice. Take notes on your brew ratios, taste and play with different concentrations and see what you like with different coffees and roast profiles. If you tend to lean towards lighter roasted coffee, you will find going past a 1:2 ratio can improve flavors and aid extraction in less soluble coffees. I really love a 1:3 ratio for lighter roasts and turbo shots. If you are more partial to darker roasts 1:2  ratio or even as low as 1:1.5 can produce some incredible flavors.

So, now when you hear someone say they’re dialing in, or playing around with their coffee recipe, you know what they mean!

Until next time…. 

Lars and the team