Grind Size and Brew Time: Changing One Thing at a Time
The same beans and water can taste very different depending on how coarse the grounds are and how long water stays in contact. This article explains how grind size and brew time affect extraction and the order to adjust when the cup is not right.
1. What grind size does
Finer grounds expose more surface to water, so flavor compounds dissolve faster. Coarser grounds expose less surface, so extraction is slower and lower. With everything else equal, finer tends to extract more and coarser tends to extract less.
In methods where water passes through the bed, grind also changes flow: finer grounds slow the drain and lengthen contact time, coarser ones drain faster. Grind and time are linked — changing one moves the other.
2. General direction by method
- Cold brew (long immersion): very coarse
- French press (immersion): coarse
- Pour-over (water flows through): medium to slightly finer than medium
- AeroPress: a wide range from fine to medium depending on the recipe
- Moka pot, espresso: fine
Exact size depends on the grinder and the beans, so a single number is not reliable. Treat the list as a starting point.
3. The order to adjust
- Sour and thin may mean under-extraction. Try grinding one step finer, raising the water temperature slightly, or lengthening the time.
- Bitter and dry may mean over-extraction. Try one step coarser, slightly cooler water, or a shorter time.
- If strength is the issue, change the coffee-to-water ratio rather than the grind.
The key is to change only one thing at a time. If you change grind, temperature and time together, you cannot tell what changed the taste.
4. Uniformity of the grounds
If grounds are uneven, fine dust can over-extract while large particles under-extract, so one cup can taste both sour and bitter. Burr grinders, which crush between two surfaces, are generally known to produce more uniform particles than blade grinders. Some people sift out the fines after grinding.
5. Records that work across grinders
Dial numbers mean different things on different grinders, so you cannot copy someone else's setting. Keep your own notes:
- Coffee weight, water weight, ratio
- Water temperature and brew time
- Grinder setting
- Taste notes (sour, bitter, sweet, and so on)
Use the ratio calculator and the 4:6 timer on this site to fix ratio and timing, then vary only the grind and compare.