No grinder produces one size. It produces a distribution — a range of particle sizes around a target.
Why the spread matters
Extraction depends on surface area. Small particles extract fast; large ones extract slowly.
A wide distribution means fines over-extract while boulders under-extract, in the same brew. That tastes bitter and sour at once, and no adjustment fixes it — every setting is wrong for part of the coffee.
A narrow distribution means most particles extract at a similar rate, and the cup is clean.
Unimodal and bimodal
Most grinders produce a bimodal distribution: a main peak at the target size and a second, smaller peak of very fine particles.
Those fines come from the bean fracturing along cell boundaries and are largely unavoidable. Better grinders produce fewer of them.
A truly unimodal distribution — one peak, no fines — is the goal and nothing achieves it perfectly.
What this means practically
Blade grinders produce an extremely wide distribution, since they smash rather than cut. This is why they cannot make good espresso, and why press coffee from one is muddy.
Burr grinders cut to a set gap and are far narrower.
Better burrs, better alignment, better geometry narrow it further.
Why it justifies the spend
This is the whole grinder argument. Every other variable — dose, temperature, ratio — you control precisely and for free. Particle distribution is the one thing only money buys.
Last reviewed 8 August 2026