How Much Coffee Grounds Should an 18g Basket Really Hold?

An 18-gram portafilter basket often cannot take a full 18 grams of grounds, and the filled portafilter then resists locking into the group head. The cause is dose, not the gasket: too much coffee leaves no headspace, so the tamped puck presses straight against the group head.

Group heads protrude outward and extend slightly into the basket when locked, which is why baskets list a recommended dose. Following the marked dose when you make coffee with a coffee machine keeps that space free. Grind setting then shows up in the extraction flow, which indicates whether the grounds are too coarse or too fine.

Many coffee enthusiasts have encountered this confusion when making espresso: they are clearly using an 18-gram portafilter basket, yet it cannot hold 18 grams of coffee grounds, and after tamping, the portafilter is difficult to lock onto the group head. In this article, Front Street Coffee analyzes the delicate relationship between basket capacity and dose through a friend's personal case, and explains the importance of the group head's protruding structure and headspace. At the same time, the article will also share how to judge whether the espresso grind setting is appropriate based on the extraction state, as well as the correct way to assess coffee grind size, helping you make stable espresso at home.

Front Street Coffee once encountered a question raised by a friend that left a deep impression. After he tamped the coffee grounds into the portafilter basket, the portafilter was always difficult to lock into the group head, and sometimes it could not be locked in at all. Even after repeatedly adjusting the dose, the situation did not improve noticeably.

When first hearing this description, Front Street Coffee suspected it might be a problem with the coffee machine's gasket—new gaskets are relatively tight, so there can indeed be some resistance when locking in. However, after this friend sent a photo, Front Street Coffee immediately understood where the crux lay: the dose was too full.

It turned out that because too much coffee powder was used, the tamped puck directly pressed against the group head, which was why the portafilter could not lock in smoothly. Normally, after coffee grounds are compacted into a puck in the basket, there should still be some space left inside the basket. Most coffee machine group heads use an outward-protruding design, and when the portafilter is locked onto the group head, part of the group head extends into the basket. This is precisely why baskets need to limit the recommended dose, in order to reserve this space. Front Street Coffee suggests that in daily use, it is best to follow the recommended dose marked on the basket.

The above content is compiled by CoffeeHunters, a coffee news website.