How concentrated the brewed coffee is — measured as TDS (total dissolved solids), the percentage of dissolved coffee mass per gram of liquid in your cup. A typical filter coffee lands between 1.20 % and 1.50 % TDS. Espresso lives at 8–12 %.
Strength is what your tongue calls "intensity." A 1.5 % cup feels heavier and more flavor-saturated than a 1.2 % cup of the same coffee. Neither is right or wrong — it's preference. Scandinavian filter culture aims for higher strength on lighter roasts; large-format Chemex and big-water Hario brewers tend to land softer.
Strength vs. extraction
Two different numbers, and the single most useful distinction in brewing: strength is concentration in your cup, extraction is how much of the bean you pulled out. They move with different levers.
- Less water for the same dose → stronger cup, similar extraction.
- Less coffee for the same water → weaker cup, also similar extraction.
- Finer grind, same dose and water → both stronger and more extracted.
How to change strength
Adjust your brew ratio. 1:14 is stronger than 1:16 is stronger than 1:18, with everything else held still. If you grind and time correctly the cup is well-extracted at any of those — the difference is just how dense the result is.