We Used Particle Analysis (And Lots of Sipping) to Find the Best Coffee Grinders

Particle size analysis of coffee grinds is not a cut-and-dried test: It’s more a clue as the the probable character of a brew. Patterns begin to emerge that correlate to the experiences I’ve had tasting coffee from each grinder. Taste is the ultimate test, alongside consistency of finicky espresso pulls. But quantitative analysis helps me (and you) actually trust and maybe understand those sensory test results.

When looking at these bar graph curves below, there are also a few rules of thumb. Big boulders north of a thousand microns will often lead to muddier character. Too many fines below 100 microns might lead to bitterness. A tight particle size distribution is associated with greater clarity of flavor. Look at the standard deviation (SD) for a clue as to overall precision: Smaller numbers indicate likely greater clairty. This said,a broad distribution of coffee ground sizes can also lead to better body, and more perceived sweetness.

Our top pick for most people, the Baratza Encore ESP, proved itself to have quite precise results at very fine grinds—with standard deviation below 200 microns on espresso grinds, and 30 percent of particles concentrated within a single range. At its price range, this is admirable precision matched by very few grinders.

Courtesy of Matthew Korfhage

The same wasn’t as true at pour-over coffee settings for the Baratza Encore ESP (seen here at setting 22), which showed a broader and more heterogeneous particle size distribution—with both small and large particle sizes. In practice, this led to a full-bodied and rounder cup, but with a little bit less of the precise aromatics one can get from our favorite grinder for drip, the Fellow Ode Gen 2.

Courtesy of Matthew Korfhage

The Ode showed a characteristic Bell-curve shape, surrounding a single high peak, which corresponded with the precise aromatics I taste when brewing drip or pour-over coffee using the Ode.

Even greater precision was on display with the Technivorm Moccamaster KM5, a flat burr grinder that showed precise results across the board—rivaling the Encore ESP at fine grinds and the Ode Gen 2 at grinding for drip. It’s not as user-friendly as some of the top-pick devices, and the resulting brews can sometimes feel clinically clean, with a thinner body. But my lord it does offer clarity.

Courtesy of Matthew Korfhage

The Kingrinder K6 hand grinder, our top manual grinder pick,, also showed strong peaks at grind sizes appropriate for pour-over coffee. Shown here are analyses of two medium-fine grinds, at 60 and 70 clicks from zero, respectively. Hand grinders have a secret weapon, which is that they cause you to grind slowly—which works very well at coaxing out more clarity from conical burrs. For pour-over grinds, the Kingrinder showed a higher peak than basically any grinder I tested, meaning grinds are very concentrated in a tight range of sizes: as many as 40 percent of coffee grounds were functionaly the same size, and about 70 percent were grouped tightly around this. This leads to quite pronounced, intense flavor notes.

Courtesy of Matthew Korfhage

At grind sizes suitable for espresso, the Mazzer Philos bests this precision, with more than 90 percent of coffee grounds huddled in a tight grouping while using the i200D burr set. Nonetheless, while boulders are all but nonxistent, enough coffee fines exist to give each shot an almost syrupy consistency. The result is both body and perceived sweetness, with a surprisingly delicate clarity. While I haven’t tested the i189D burrs also available as an option, reports from the world say that the 189Ds lean even harder into clarity of flavors. But note that at bigger grind sizes more suitable for drip coffee, you’ll get a quite broad distribution. This will lead to a well-rounded cup, but may not offer the clarity of flavor of the Fellow Ode Gen 2 or the Kingrinder K6 for drip and pour-over brews.

Omni via Matthew Korfhage

Omni via Matthew Korfhage

WIRED tests coffee grinders by grinding a lot of beans, and making a lot of coffee—testing each grinder to see if it can serve well for espresso, Aeropress, drip or pour-over coffee, and coarse-ground cold brew and French Press. I tend to always grind a drip Stumptown Homestead or Single-Origin Colombia as a baseline, because each is readily available at my local supermarket with stamped roast dates, and because I know the flavor well enough I can detect variations. But I’ll also try out a number of flavors and roasts on each grinder, for different brewing methods.

Photograph: Matthew Korfhage

We assess each grinder for decibel level while grinding, ease of cleaning and operation, hopper design, the presence or absence of “popcorning” (where the beans pop around inside the hopper, often leading to more uneven results), messiness and static electrical buildup, grind retention, ease of use, value, and simple aesthetics.

Previous WIRED reviewers assessed grind uniformity visually with the aid of macro lenses, or filtered coffee grounds with sieves. In the most recent round of testing, I re-assessed each top coffee grinder pick using particle grind size analysis, with the help of the DiFluid Omni roast color and particle size analyzer, as well as a data analysis app that’s still in beta testing.

I tested both fine and medium grinds on each grinder, using the same beans for each grinder, roasted within a month of testing. I repeated the particle analysis at least five times for each grinder and setting. I assessed the uniformity of the grind and the overall distribution of particle sizes—paying particular attention to the share of coffee fines (the tiniest particles smaller than 100 microns) and boulders (big coffee bits larger than 1000 microns).

The reasons are simple: Flavor. Freshness. Aroma.

Whenever you open a vacuum-sealed bag of beans, a little invisible clock starts. Oxidation begins to erode the character of your beans, breaking down organic compounds and degrading them, turning your lovely beans to cardboard. Aromatic flavor compounds also escape from the bean, gassing out into the air where they do no particular good.

When you grind your beans, these processes goes into overdrive. Freshness for whole beans can be measured in weeks. For ground beans, freshness in the open air is a matter of hours or even minutes. That bag of pre-ground beans you got from the supermarket? It’s still coffee, of course, and it’ll taste like coffee. But the vibrancy is gone. As far as true freshness is concerned, that coffee’s been dead for weeks. (Pre-ground beans can be kept airtight for a week or so and maintain their flavor, if you get them ground fresh at a coffee roaster.)

Photograph: Matthew Korfhage

The only reliable way to get truly excellent flavor from your coffee beans, the way you experience it at a café, is to use fresh, whole beans. This is also how you can exercise some control over extraction, and dial in your brewer or espresso maker to get the pefect results for each bean.

Espresso requires a fine grind, pour-over a little coarser, electric drip coffee a little coarser than this. Each grinder should have a guide to the best adjustments for each brewing method. Lighter-roast beans will want a finer grind than dark-roast, to aid in extraction: porous dark-roast beans give up their secrets a lot easier.

It’s all kinda fun to figure out, if you let it be fun. But certainly, when you strike paydirt, you’ll know it: Finding the right marriage of grind and bean, on a good grinder, can turn into the best cup you’ve ever had. It’s like the magical first time you seared a perfect steak, or baked a perfect layer cake. Effort meets reward. It’s marvelous. The grinders in this guide will help you find that moment more often.

Photograph: Iryna Veklich/Getty Images

Most coffee grinders fall into three main types: Conical-burr, flat-burr, and blade grinders. Burr grinders are generally higher quality, and higher cost.

Conical-burr grinders are the category occupied by our top pick, the Baratza Encore ESP, and pretty much all of the most affordable grinders that still make good coffeee. And there’s a reason for this: Conical tends to offer the sweet spot at the intersection of high-performance, cost, and flexibility. In a conical grinder, coffee beans are crushed and ground between two rings of burrs. They deliver a finer, much more consistent grind than you’d get with a traditional blade grinder, even the nicest blade grinder you ever met. Conicals do tend to throw off more fines than a flat burr, but many feel this leads to more body and a more rounded flavor character.

Flat-burr grinders are more precise than conical grinders, but they’re also typically more finicky and also more expensive. Burrs are laid on top of each other, and the beans pass through them as they grind. The grinder action pushes the grounds out of one end, instead of relying on gravity like a conical-burr grinder, which means the beans spend more time in contact with the burrs. This results in a more consistent grind, down to the micron in some cases, which leads to very precise flavors. For this reason, flat-burr grinders are often preferred as a way to elicit very precise flavors form single-origin beans for pour-over, drip, and Aeropress.

Blade grinders have a chopping blade that spins around like a food processor. But blades don’t produce even results. Some of your coffee will be fine powder at the bottom, and at the top you’ll have bits too large for even French press. The result is an inconsistent, unpredictable brew. These grinders are generally quite cheap.

But in case you’re wondering, using fresh beans in a blade grinder is still way better than buying ground coffee. (You can learn how to shake the beans to even your grind just a little. Pulsing the machine often also works. See world barista champion James Hoffmann’s video for some more blade grinder hacks.) Still, if you can afford it, the conical or flat-burr grinders on this list will lead to far better coffee than any blade.

The machinery in a high-quality burr grinder is a bit more complicated, and it’s built to withstand greater wear and tear. In cheap burr grinders, the burrs can get blunt from regular use, and flimsier motors may burn out in a matter of months.

But also, coffee grinders have undergone a revolution in technology and consideration in the past decade. Manufacturers have been experimenting with different shapes of burr even on conical burr grinders—pentagonal, hexagonal, heptagonal. And grinders with more precision cuts will cost more money.

Flat burrs also cost more money to manufacture, and are seen as having more precision. The true geeks are swapping out to new generations of flat burr that offer greater precision in machining, and multistage grinds. Grinder makers are experimenting with larger and smaller burrs, and different materials. It’s a hive of invention out there. And these precision parts cost money: Some burr sets might cost hundreds all by themselves.

The end result of all this attention is a greater range or finer adjustment of grind sizes, better and more reliable calibration, and often more precision in the resulting coffee grinds—and thus more precision in the flavor of your coffee or the brew of your espresso.

No, please don’t do this.

First off, if you’re trying to improve the flavor of store-bought beans, the game’s already lost. One of the main reasons to use fresh-ground whole beans is to avoid oxidation, and pre-ground beans have already been cardboarded up by evil, stale air.

But also, you’ll mostly just muck up your machine. Logically, it might make some sense. Your grind is too coarse, so let’s just run them through again at a finer setting, and perfect coffee results! Alas, on burr grinders, pre-ground coffee will get stuck inside the burrs, gum them up, and cause you to have to take the whole thing apart and clean it with your little brush and put it back together.

Quite simply, the best coffee grinders for espresso are the ones that offer the finest calibration at the “fine” end of the spectrum. If you want to get super specific, look for coffee grinders that offer a number of fine calibrations at the fine end of the spectrum.

Dialing in individual espresso beans can require quite fine adjustments—and so even if a grinder is technically able to grind fine enough for espresso, it should also be able to make precise enough adjustments within that range to account for different beans, roasts, and machines. (For a real-world counterexample, witness the wall WIRED reviewer Joe Ray ran into when trying to get the (excellent) Wilfa Uniform Coffee Grinder to work for espresso. Without fine adjustments, chances are you’ll fail.)

Otherwise, what you’re looking for is excellent build, a motor that can withstand the higher torque you’ll need to grind finely even on lighter roasts, and a machine that deals well with static electricity: Finer espresso grinds can turn static into a terrible enemy, sending coffee grounds spraying wildly.

The most vaunted espresso grinders can travel upwards into the high hundreds of dollars (see the Timemore Sculptor 064S flat-burr) or the thousands of dollars (see the Zerno Z1).

The Mazzer Philos Coffee Grinder ($1,500) offered maybe the best shots of espresso I’ve pulled at home in the past year. This offers delicate flavor and syrupy shots like the ones you’ll get from a cafe, even on lower-cost espresso machines. (See my full review of the Mazzer Philos.)

But in this guide, we focused mostly on the best espresso grinders for the 90-some percent of people who are trying to gain access to good coffee without spending four figures. For most people and most budgets, our top pick, the Baratza Encore ESP ($200), will be the best choice, with sturdy construction and 30 grind adjustments for espresso alone. If you don’t mind a little elbow grease, you can tune your grinds even finer by using a manual coffee grinder like the Kingrinder K6 ($99).

And then there’s the true budget electric option. The tiny, slow-grinding Wirsh Geimori T38 Plus ($130) is the lowest-cost electric espresso grinder I’ve tried that can actually make good espresso on non-presurized baskets, though I’d probably limit it to medium roasts or darker, lest you strrain the machine. Torque is not a strong suit.