What is the best grind size for a French press?

The French press is a classic immersion brewer, meaning the coffee grounds steep in water for the entire duration of the brew—typically four minutes or more. Because the grounds are in constant contact with the water, the grind size is the most important variable for controlling extraction. If your grind is too fine, the water will extract too much from the coffee, resulting in a cup that is harsh, bitter, and difficult to press through the metal mesh filter.

Conversely, if your grind is too coarse, the water won't be able to extract enough flavor, leading to a weak, sour, or watery cup. A coarse, sea-salt-like grind provides the perfect balance. It allows the water to penetrate the grounds slowly and evenly, extracting the desired oils and sugars while leaving behind the undesirable, bitter compounds that are more easily extracted from finer particles.

Uniformity is just as important as size. If your grinder produces a mix of large chunks and fine dust (often called 'fines'), the fine particles will over-extract and create a muddy, silty texture in your final cup. This is why a high-quality burr grinder is highly recommended for French press brewing. Unlike blade grinders, which chop beans into irregular pieces, burr grinders crush them into consistent, uniform particles, ensuring a clean and balanced extraction.

In practice, if you find your French press coffee tastes muddy or leaves a lot of sediment in your mug, try adjusting your grind to be slightly coarser. If it tastes thin or sour, try a slightly finer setting. Once you find the right grind size for your specific beans and grinder, you will be rewarded with a rich, full-bodied cup that showcases the deep, complex flavors of your coffee.