Most coffee problems trace back to extraction. This guide matches common off-flavors to their likely cause and the fix.
Common problems
| Symptom | Likely cause | Fix |
|---|---|---|
| Sour, weak, thin | Under-extracted | Grind finer, hotter water, brew longer |
| Bitter, harsh, dry | Over-extracted | Grind coarser, less time, cooler water |
| Flat, stale, dull | Old beans or grounds | Use fresh beans, grind just before brewing |
| Watery, no flavor | Ratio too weak | Add coffee or reduce water |
How to fix it
Change one variable at a time so you can tell what worked. Grind size is usually the most powerful lever, followed by ratio and water temperature.
Sour means more, bitter means less. Sour coffee is under-extracted, so extract more (finer grind, longer, hotter). Bitter coffee is over-extracted, so do the opposite.
See the Extraction Yield Chart and the Coffee Strength Formula.