How to choose a coffee grinder?

Picking a grinder rests on four criteria: burr type (flat or conical), burr diameter (typically 40, 58, 64, 83 or 98 mm), target method (espresso, filter, or versatile), and internal retention. A grinder that shines for one method rarely matches it on the next — anchor the purchase to your primary use.

The single most consequential choice is conical versus flat burrs. Conicals (two nested cones, with grounds falling by gravity) produce a bimodal particle distribution: lots of mid-sized particles plus a higher share of fines that bring body and sweetness to espresso. Flat burrs (two opposing discs, grounds ejected radially) yield a more unimodal distribution: more clarity, sharper aromatic separation, a natural fit for filter. This difference, documented by laser-diffraction studies published by Mathieu Theis (Eureka) and referenced across barista literature, explains why home espresso grinders lean conical (Niche Zero, Mazzer) while high-end filter grinders lean flat (Mahlkonig EK43, Weber Workshops).

Burr diameter drives cutting geometry, grinding speed and heat generated. A traditional commercial espresso grinder spins at 1,400 rpm with 64-83 mm burrs. A 'low-speed' grinder (400-600 rpm) cuts the heat transferred to the coffee and the volume of fines. Large diameters (83-98 mm) are the reference for professional filter grinding: the bigger cutting surface allows lower rpm and a tighter distribution. For home use, 58-64 mm is a solid compromise.

Internal retention — the coffee that stays trapped in the chamber between doses — is a long-underrated criterion. A grinder with 3-5 g of retention forces you to purge at start-up (throwing away 2-3 g of stale ground coffee) and blurs profiles when you change beans. Modern single-dose grinders, popularised by the competition scene since 2015, bring retention below 0.3 g through angled chambers and a burst of compressed air. For an enthusiast who rotates single origins weekly, that feature is life-changing.

Finally, adjustment control: stepped (discrete clicks, usually 40 to 60) or stepless (continuous variation). For espresso, where one or two seconds can swing an extraction from under to over, stepless is preferable. For filter, stepped is plenty. In Belgium, specialty roasters in Brussels, Ghent, Antwerp and Liège equip their shops with EK43-class filter grinders and, at the same time, sell whole beans that will require a well-calibrated grinder at home — personalised advice at the counter is the best starting point.

Grinder choice criteria