How many grams of coffee should I use for a double shot?

The 'double shot' is the industry standard for espresso, but the amount of coffee used—the dose—can vary significantly. In the past, a double shot was often defined by a fixed volume, but today, we measure by weight. Using a scale is non-negotiable if you want to achieve consistent results. The dose you choose should be dictated by the capacity of your portafilter basket and the density of your coffee.

If you use too little coffee, you will have too much 'headspace' between the puck and the shower screen. This can lead to uneven water distribution and channeling, where water flows through the puck in streams rather than evenly. If you use too much coffee, the puck will press against the shower screen, which can also cause channeling and make it difficult to lock the portafilter into the group head.

Roast level also plays a role in your dose. Because dark roasts are less dense, they take up more volume in the basket than light roasts. You might find that you can fit 18 grams of a light roast comfortably, but 18 grams of a dark roast might be overflowing. In such cases, you may need to adjust your dose slightly—perhaps down to 17 grams—to maintain the correct headspace.

In practice, start with the manufacturer's recommendation for your basket size. If you have an 18-gram basket, start there. Once you have your dose, keep it consistent. If you need to adjust your extraction, change your grind size or your yield (the weight of the liquid espresso), not your dose. By keeping your dose constant, you eliminate one of the most common sources of inconsistency in espresso brewing.