It's a fantastic question, and the answer truly separates a standard cup from a truly exceptional one. While the provided context doesn't offer specific details, we can dive into what defines a shot of espresso.
You'll often hear that a single shot of espresso is about one fluid ounce (30 ml), and a double shot is two fluid ounces (60 ml). While this is a decent starting point, to really understand and control the quality of your espresso, you must move beyond thinking in terms of volume and start thinking in terms of weight. The beautiful, aromatic crema that sits on top of a fresh shot is mostly air, which can make measuring by volume very inconsistent.
The most precise and repeatable way to measure a shot of espresso is by weight, using a concept called a "brew ratio." This is the ratio of the weight of the dry coffee grounds you use to the weight of the liquid espresso in your cup. The modern industry standard for a balanced, delicious shot is a 1:2 ratio.
This means for a typical double shot, which is what most cafes serve as their default, a barista will use around 18 to 20 grams of finely-ground coffee to produce a 36 to 40-gram shot of liquid espresso. This is the amount that truly matters. So, while it may look like two ounces in a glass, the key to its flavor and consistency is its weight. By focusing on the brew ratio, you guarantee a perfect shot every single time.
