The Impact of Coffee Grind Size on Flavor: How to Determine Grind Size for Pour-Over, French Press, Cold Brew, and Espresso

Why is my coffee so weak? Why does my coffee taste bitter and astringent?!

Is there something wrong with my brewing technique? No, it's your grind size that's the problem! The grind size of coffee beans determines the dissolution rate of soluble flavor compounds in the coffee. Of course, not all soluble substances in coffee are delicious. Therefore, to maximize the extraction of delicious flavor compounds while avoiding the extraction of undesirable ones, determining the appropriate coarseness of coffee particles becomes extremely important.

Different coffee brewing methods require different grind sizes

Different coffee brewing methods require different degrees of grind due to differences in their extraction methods. Taking the most commonly encountered pour-over coffee, French press, espresso machine, and cold brew/ice drip as examples, their coffee grind degrees from coarse to fine are arranged as: [French press > pour-over coffee > cold brew/ice drip]. Due to differences in extraction water temperature, method, and time, it's necessary to find the appropriate grind degree for each extraction method to achieve properly extracted coffee concentration.

However, since grinders don't have fixed scale values, each grinder produces particles with different degrees of coarseness. At this point, we need to purchase a cupping calibration sieve (which is the No. 20 Chinese standard sieve with an aperture of 0.85mm).

How to use coffee grind calibration sieve?

The No. 20 Chinese standard sieve has an aperture of 0.85mm and is used as a tool for particle size classification and particle size detection. As long as it meets factory standards, the standard sieve is accurate. Coffee grind calibration is also very simple—just pour the ground coffee powder into the sieve, cover it with the lid, shake it horizontally until no more particles fall through, then weigh the particles that passed through the sieve. This way, you can determine the coarseness of the grind. For example, if you grind 10g of coffee powder and 7.5g passes through, then this grind size has a 75% pass rate through the No. 20 sieve. The higher the pass rate, the finer the coffee grind.

How to determine if the coffee powder coarseness is suitable for your brewing method?

FrontStreet Coffee conducts cupping whenever we get each new batch of beans. The main purpose of cupping is to determine flavor profiles and ensure quality control of coffee beans without interference from brewing techniques. Since cupping uses high-temperature immersion for coffee extraction, the grind size cannot be too coarse or too fine. FrontStreet Coffee uses a grind size with a 70-75% pass rate through the No. 20 sieve for cupping. Since cupping can rely on standard sieves for calibration to determine grind size, we can also use sieves for calibration in other brewing methods (except for espresso extraction).

Suitable coffee powder grind size for French press extraction: 68-75% pass rate through No. 20 sieve

The extraction method of French press is very similar to cupping, both being primarily immersion-based. Therefore, the chosen grind degree highly overlaps with that used for cupping. There's another reason for choosing coarser grind particles—French press filtration uses a metal filter with visible gaps, so choosing a coarser grind helps with better filtration. Coffee beans with different roast levels will have different optimal grind sizes. FrontStreet Coffee suggests that medium-light roast coffee beans (with acidic flavors) can use medium grind (72-75% pass rate), while medium-dark roast coffee beans (with less acidity) can use medium-coarse grind (68-71% pass rate).

Suitable coffee powder grind size for pour-over extraction: 70-80% pass rate through No. 20 sieve

Pour-over coffee is primarily drip-filter based. Unlike immersion methods, this has a shorter extraction time, making it less likely to extract undesirable flavors. Pour-over coffee brewing time is short, approximately 1 minute 30 seconds to 2 minutes 30 seconds. Therefore, it needs to be finer than cupping grind size to fully express the coffee's flavor. FrontStreet Coffee suggests that medium-light roast coffee beans (with acidic flavors) can use medium-fine grind (75-80% pass rate), while medium-dark roast coffee beans (with less acidity) can use medium grind (70-75% pass rate).

Suitable coffee powder grind size for cold brew/ice drip: 75-80% pass rate through No. 20 sieve

Unlike pour-over or French press, cold brew/ice drip uses low-temperature immersion extraction. Low-temperature extraction extracts significantly fewer bitter and astringent substances. By extending extraction time and fully saturating the coffee powder, it's easier to extract small molecular flavor compounds such as floral and fruity notes. However, since both brewing methods require long extraction times, if the grind is too fine, the cold brew coffee can become cloudy and develop woody flavors, while ice drip may experience powder layer buildup/blockage. FrontStreet Coffee suggests that both medium-light roast and medium-dark roast coffee beans can use medium-fine grind (80-85% pass rate).

Suitable coffee powder grind size for espresso machines (this cannot be calibrated using sieves because it's too fine)

FrontStreet Coffee's stores calibrate espresso every day before opening, with a significant portion of this process involving adjusting the grind size. Since espresso machines are extremely sensitive to coffee powder coarseness, even a difference of 0.1 on the grind scale can result in different extraction times and flavors. Taking FrontStreet Coffee as an example, our espresso extraction recipe is 20g of coffee powder to extract 40g of coffee liquid in 28 seconds (with ±1 tolerance). We first fix this extraction recipe, then adjust the grind size to achieve this extraction target. Afterward, we taste the flavor to determine if parameters need fine-tuning.

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Important Notice :

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FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473