Published by HomeGear Drip · Reviewed against our data methodology
Conical vs Flat Burrs: How to Read an Espresso Grinder Spec Sheet
Burr shape, burr diameter, and stepped vs stepless adjustment are the three specs that decide whether a grinder can make espresso at all. Here is what each one changes, and what it does not.
For a semi-automatic espresso machine, the grinder matters more than the machine. That claim gets repeated so often it has stopped meaning anything, so here is the concrete version: espresso needs a grind fine enough and even enough to build resistance against nine bar of pressure. A grinder that cannot adjust finely enough, or that produces too wide a spread of particle sizes, will produce a sour, fast, thin shot on a machine that cost five times as much.
Which means the spec sheet is worth reading properly. Three numbers do most of the work.
Burr shape: conical vs flat
Conical burrs are a cone spinning inside a ring. Coffee falls through by gravity, which means they need less motor power, run cooler at low speed, and retain relatively little coffee between doses. They tend to produce a slightly wider particle distribution — a mix of fines and larger particles — which many people describe as a heavier, sweeter, more forgiving shot.
Flat burrs are two parallel rings facing each other. Coffee is thrown out through the gap centrifugally. They tend to produce a narrower, more uniform particle distribution, which shows up as clarity and separation in the cup, and they are generally more sensitive to dialing in. They usually cost more to make, hold more coffee inside, and want a bit more cleaning attention.
Neither is better. They are different flavor profiles, and the choice is genuinely preference. In this catalog the Baratza Encore ESP and Capresso Infinity are conical; the Eureka Mignon Specialita and Fellow Ode Gen 2 are flat. What matters more than shape is the next spec.
Burr diameter: the one that scales with money
Larger burrs grind a dose in fewer rotations, which means less heat, less time, and usually a tighter particle distribution. This is where grinder money actually goes. A 40mm burr set and a 65mm burr set can carry the same brand name and the same shape and behave nothing alike — compare the Eureka Mignon Silenzio against the larger-burred Eureka Atom Specialty 65.
Diameter is the one grinder spec where "bigger is better" is broadly true, which is why our comparison tool does flag the larger burr set as the winner in a head-to-head.
Adjustment: stepped vs stepless
This is the spec that decides whether a grinder can do espresso at all.
Stepped grinders click between fixed positions. If the steps are coarse — as on most general-purpose drip grinders — you can land on either side of a good espresso shot with nothing in between. That is the single most common reason a grinder "can't make espresso."
Stepless grinders adjust continuously, so you can move a hair finer without committing to a whole step. Most dedicated espresso grinders are stepless or use very fine steps in the espresso range specifically. The Eureka Mignon line and the DF64 are stepless; the Baratza Encore ESP uses steps deliberately tightened in the espresso range.
If a grinder's spec sheet gives a step count but does not say the steps concentrate in the fine range, treat that as a question to answer before buying, not a detail.
Two things the spec sheet will not tell you
Retention is how much ground coffee stays inside the grinder between doses. High retention means today's shot contains some of yesterday's coffee, and it makes single-dosing — weighing in exactly what you want to grind — frustrating. "Single dose" in a product name, as in the Eureka Mignon Zero or the DF64, signals a design built to minimize it. Manufacturers rarely publish a retention figure.
Whether it doses by weight or by time. Time-based grinders run the motor for N seconds, so the dose drifts as beans age and the burrs load differently. Weight-based grinders — the "W" and "Libra" style models, like the Baratza Sette 270Wi and Eureka Mignon Libra — weigh the output and stop. That is a real workflow difference that no burr spec captures.
Hand grinders are not a compromise
A well-made hand grinder can hold its own against electric grinders costing several times more, because you are paying for burrs and bearings rather than a motor and a housing. The tradeoff is entirely effort and speed: about 30-60 seconds of cranking per double shot. The 1Zpresso J-Ultra, K-Ultra, and X-Ultra are built for espresso-range adjustment specifically.
For one or two drinks a day, this is a genuinely sensible way to spend a grinder budget. For a household making six, it is not.
Reading a spec sheet in order
- Can it adjust finely enough for espresso? Stepless, or steps concentrated in the fine range. If no, stop here.
- How big are the burrs? This is where the money goes and what scales grind quality.
- Conical or flat? Pick the flavor profile you prefer; neither is a mistake.
- Does it dose by weight? A convenience feature, but a large one if you make several drinks a day.
Compare any two grinders side by side in the comparison tool, see all coffee grinders, or start from which machine type fits you.
Prices shown on our espresso product pages are manufacturer list-price baselines, not verified live retailer offers. Confirm the current price, stock, and warranty terms with the seller before buying. See our methodology.
Frequently Asked Questions
Semi-automatic or super-automatic — which should I buy?+
A semi-automatic gives you the portafilter, the grinder choice, and control over dose and timing, which is what you want if the process is part of the appeal. A super-automatic grinds, tamps, brews, and froths behind a closed door for one button press, which is what you want if the drink is the point. The machines cost about the same at the middle of the market; they differ in how much of the work you do.
Do I need a separate grinder?+
For a semi-automatic, yes — an espresso grinder matters more than the machine, because espresso needs fine, evenly adjustable grind that a general-purpose blade or coarse burr grinder cannot deliver. Super-automatics and a few "all-in-one" semi-autos have a grinder built in, so no separate purchase is needed.
Is 15 bar of pump pressure better than 9?+
No. Espresso is extracted at about 9 bar at the puck; 15 bar is the pump's maximum rating, not the brew pressure, and nearly every consumer machine on the market is rated the same 15 bar. It is not a spec that separates machines, which is why we do not score it as a winner in comparisons.