Burr grinders use one of two main burr geometries: conical or flat. Both are used in everything from entry-level home grinders to high-end commercial machines, and they produce subtly different cups.
Conical burrs
Conical burrs feature an inner cone-shaped burr fitting inside an outer ring burr. Coffee is fed through the gap between them. The motor typically runs at lower RPM, which keeps grind temperatures down.
Cup character: tends toward more body and a heavier mouthfeel. Slightly more variation in particle size compared to flat burrs, which creates a fuller, more rounded cup. Often described as forgiving, smooth, and complex.
Notable conical grinders: Niche Zero, Baratza Encore, Comandante, Mahlkonig EK43 has a flat version but the K30 used a conical.
Flat burrs
Flat burrs are two parallel disks that grind coffee in the gap between them. The motor often runs at higher RPM. The geometry produces a tighter particle size distribution.
Cup character: tends toward more clarity, separation of flavor notes, and brightness. The narrower particle range means more uniform extraction, which highlights individual flavor notes rather than blending them. Often described as analytical, articulate, and clean.
Notable flat grinders: Mahlkonig EK43, Eureka Mignon series, DF64, Lagom P64.
What matters more than geometry
Burr quality, alignment, and burr design (cutting geometry, coating) all matter more than conical vs flat. A high-quality conical grinder will out-grind a poorly made flat grinder, and vice versa.
For most home brewers, the choice between conical and flat is less important than choosing a grinder that fits your budget and brewing methods.
Practical guidance
If you mostly brew espresso and value clarity in lighter roasts, lean flat. If you brew a mix of pour-over and espresso and want versatility, lean conical. If you cannot try both before buying, go with the geometry of the grinder that has the strongest reputation in your price range, regardless of which it is.