The flat-versus-conical argument is real and it is usually overstated.
Flat burrs
Two parallel rings, coffee ground between the faces.
Tendency: a narrower particle distribution, producing a cleaner, more separated, more acidic cup with a lighter body.
Trade-offs: higher retention, more heat generated, usually more expensive, and they need more power.
Conical burrs
A cone inside a ring, coffee ground in the annular gap.
Tendency: a slightly wider distribution with more fines, producing more body and a rounder, more blended cup.
Trade-offs: lower retention, cooler running, cheaper, and they feed by gravity so they need less power.
How big is the difference
Smaller than people claim. A good conical beats a mediocre flat comfortably, and vice versa.
Burr quality, size, alignment and geometry matter more than the shape. A 64 mm flat and a 64 mm conical of similar quality produce cups that differ subtly.
For filter specifically
Flat burrs suit light roasts and clean methods where clarity is the point.
Conical burrs suit medium roasts, French press and espresso where body is welcome.
Neither is wrong.
What actually to buy on
Alignment quality, burr size, adjustment resolution, and retention. Those determine the result far more than the geometry.
If two grinders are otherwise equal, pick the one you can afford to align well.
Last reviewed 8 August 2026