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An espresso contains on average 30 millilitres of coffee. That’s enough for an intense, full coffee shot packed with flavour. But where does that amount come from? And how many ml are in a double espresso or a ristretto? Here you’ll read how those volumes are determined and why the millilitres have more impact than you might think.

What determines the amount of an espresso?

The amount of espresso is determined by the ratio of ground coffee, pressure, temperature and extraction time.

An espresso isn’t just any amount of coffee, but the result of a precise process. According to the guidelines of the Specialty Coffee Association, you use about 18 to 20 grams of finely ground coffee, from which in 25 to 30 seconds under 9 bar pressure about 30 millilitres of concentrated coffee is extracted.

How finely you grind the coffee, how hard you tamp, how hot the water is and how long the water flows through: all these factors determine whether your shot ends up at 25 ml or closer to 35 ml. More water

For the advanced barista, the extraction time of an espresso is much more than just a number. It’s a direct gauge for extraction and therefore for flavour. An espresso that runs through too quickly or too slowly is rarely in balance, with a bitter, sour or watery coffee as the result. But what IS the ideal time? And how do you adjust your grind, tamping or dose accordingly?

What is extraction time?

The extraction time, also called brew time, is the time the water needs to flow through the ground coffee in the portafilter, from the moment you press the espresso button to the last drop falling into the cup.

This time is always measured in seconds, usually with a stopwatch or a built-in timer in the espresso machine.

Important: extraction time isn’t the same as warm-up time of the machine or pre-infusion.

What is the ideal extraction time for an espresso?

The guideline for a classic espresso is between 25 and 30 seconds.

But this depends on:

• The amount of coffee (standard: 18-20 grams)
• The