Granulometry in Coffee: What does “Screen Size” really mean?

In the field, every coffee bean tells a story: the variety planted, the climate, the altitude, and the farmer’s care during harvest. All of these factors influence its size and shape what we technically call granulometry. While this is the precise term, in practice most of the industry simply refers to it as screen size, since classification is done with metal sieves that separate the beans according to their diameter. That’s why we often hear about “screen 18” or “screen 14/15” coffees descriptions that help us better understand the physical characteristics of a lot.

The importance of this measurement begins on the farm but extends to those who will later work with the coffee. A lot with good uniformity in screen retention may indicate consistency in harvesting and processing, which ultimately facilitates even roasting and a better cup expression. This is why, although granulometry does not define quality on its own, it is a valuable tool to connect the producer’s work with the needs of roasters and exporters, who seek consistency and clarity in their purchases.

It’s true that larger beans are often assumed to be better, but the reality is more complex. Traditional varieties such as Caturra or Bourbon produce medium-sized beans (commonly found in screen 14 and 15) that can deliver bright, balanced cups with remarkable complexity. For this reason, screen size should be considered a complement within the physical analysis never an automatic synonym for quality.

At Café Primitivo, we use granulometry to better understand each lot from its origin, anticipate how it will behave during roasting, and project a consistent sensory profile. In the end, what truly matters is not whether a coffee is screen 14, 15, or 18, but recognizing in every bean the story of those who cultivated it and the purpose that brought it all the way to the cup.