Why is the Espresso Brew Ratio Strictly 1:2? Must 18g of Coffee Extract Exactly 36ml?

The Golden Ratio of Espresso: Understanding the 1:2 Brew Ratio

FrontStreet Coffee believes that when you've been working with espresso for a while, you're undoubtedly familiar with the "1:2" ratio. It's often hailed as the "golden ratio" for espresso extraction, and it's the most commonly used proportion when extracting espresso shots.

The brew ratio refers to the proportion between the amount of coffee grounds used and the amount of coffee liquid obtained. For example, a 1:2 brew ratio means that for every 1 gram of coffee grounds used, you need to extract 2 milliliters of coffee liquid. To illustrate, if we use 18g of coffee grounds, following a 1:2 brew ratio would require extracting 36ml of coffee liquid. Since many bloggers refer to this ratio as the "golden ratio" of espresso (we can understand this as meaning something good), many people wonder: why must we use 1:2 for espresso extraction? Would ratios like 1:4, 1:5, or 1:6 also work?

Must espresso always be extracted from 18g of coffee grounds to yield 36ml of coffee liquid? Of course, you can! Whether using any ratio, or extracting 50, 60, 70ml of coffee liquid from 18g of grounds—or even more—is completely acceptable! It's not that espresso made with a 1:2 ratio is necessarily the best tasting. With proper parameters, regardless of which ratio you use or how much liquid weight you extract, you can achieve a delicious espresso shot. However, there's a reason why the 1:2 ratio has been dubbed the "golden ratio"—it's because this ratio can produce espresso that better meets our needs. Let's recall what the size of the brew ratio determines?

That's right! It's the concentration of coffee. FrontStreet Coffee often shares that coffee concentration is primarily influenced by water amount. With other parameters unchanged, when you use more water during coffee extraction, you'll get more coffee liquid, but the concentration will be lower, and vice versa. Below are two cups of coffee extracted by FrontStreet Coffee using the same amount of grounds. The coffee beans used are from FrontStreet Coffee's espresso bean selection—the specialty blend. Both extractions took thirty seconds, with the difference being the ratios used. One coffee has a 1:2 ratio, meaning 18g of grounds extracted to 36ml of coffee liquid; while the other uses a 1:4 ratio, meaning 18g of grounds extracted to 72ml of coffee liquid.

Through concentration measurements, we can determine their concentrations are 10.83% and 5.36% respectively—approximately a twofold difference. Both exhibit rich nutty and chocolate flavors, with the only distinction being their concentration levels. One has higher concentration, so it tastes richer and more intense; the other, due to its lower concentration, has more distinct layers and higher flavor recognition, making each have its own unique characteristics.

Why is 1:2 Considered the Golden Ratio?

It's simple—because coffee extracted with this ratio will have a sufficiently high concentration. In daily life, not many people drink straight espresso shots; most prefer to use espresso as a base for other specialty coffee drinks. For example, adding milk to make lattes or cappuccinos, or pouring espresso over milk to make Dirty, and so on.

And most specialty coffee drinks require espresso with a certain concentration level, especially those that include milk. Only when the espresso concentration is high enough will the lattes, cappuccinos, flat whites, and other coffee drinks we make have sufficient body and richness. But if the espresso concentration is too low, the resulting coffee will have a noticeable "watery" texture. While the flavor might be acceptable, the mouthfeel won't be as outstanding. (Americano works with any ratio) This is why "1:2" has become the most commonly used brew ratio for espresso extraction. Coffee extracted with this ratio not only has complete flavor expression but also maintains a sufficiently high concentration, allowing it to perform exceptionally well even when mixed with large amounts of milk.

However, everyone should know that in actual extraction, we don't need to strictly adhere to the 1:2 ratio. Ratios around this range, such as 1:1.5 or 1:2.5, are also perfectly acceptable. The 1:2 ratio is merely an indicator—it tells us that within this range, we can extract espresso with high enough concentration to make delicious specialty coffee drinks.

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