Grind size, comfortably.
The rough exchange rate
Moving brew temperature by about four degrees Celsius (7 °F) has an effect similar to one step of grind adjustment on a typical grinder.
Since a grinder gives you dozens of steps and a kettle gives you a range of maybe eight useful degrees, grind is where nearly all the control lives.
Why grind dominates
Grind size changes surface area, which is the primary driver of how fast compounds dissolve. Halving particle size roughly doubles the surface area exposed to water.
Temperature changes the rate at which dissolution happens, which is a smaller lever within the narrow band coffee is brewed in.
When temperature earns attention
Light roasts. Dense and hard, they genuinely benefit from the top of the range — 95 to 96 °C (203 to 205 °F). If a light roast is sour at 92 °C (198 °F), try hotter before grinding finer again.
Dark roasts. Already soluble, they turn bitter at high temperature. 88 to 92 °C (190 to 198 °F) suits them.
Espresso, where contact time is so short that a couple of degrees is proportionally larger. This is what a PID controls.
The order to work in
Dose and ratio fixed. Grind until the time is right. Taste. Then, and only then, consider temperature.
Last reviewed 30 October 2026