Home espresso setups often put most of the money into the machine, because it’s the impressive part. The sources this page draws on argue the other way round. Hoffmann’s advice in The World Atlas of Coffee is to upgrade the grinder first, and Jessica Easto’s Craft Coffee, written for filter brewing, says that if you buy only one piece of coffee equipment, it should be a burr grinder. This page explains why, what one large set of grinder measurements does and doesn’t show, and how to tell whether your own grinder is what’s holding you back.
Our April 2026 video covers the same ground but predates this revision; where they differ, follow the text. It repeats several claims we could not support and have removed here, among them a line attributed to Gagné that switching grinders changes flavor more than any other single variable, grinder-retention figures for the Ross Droplet Technique, and a DF64 with SSP burrs rated at 80 to 90 percent of much costlier grinders.
What the grinder decides
Water extracts coffee from the surface of each particle inward, and no grinder makes particles of one size. Easto writes that all grinders produce a distribution, from relatively large chunks to tiny fines. Scott Rao describes the consequence in Espresso Extraction: fines extract quickly and add bitterness and astringency, while boulders under-extract, lowering both extraction and strength. Hoffmann makes the same point about blade grinders: their fine powder quickly adds bitterness while the large pieces add sourness, so one brew gets both.
For espresso the stakes are higher. Hoffmann notes that variations of a few hundredths of a millimeter in grind size make a difference, and that an espresso grinder has two jobs: it must grind finely enough for good espresso, and it must be easy to adjust in very small steps. A machine can’t make up for a grinder that can’t do either; it can only push water through what’s in the basket.
That’s the basis of Hoffmann’s advice. In his words, a great espresso machine “will be a waste of money if you are pairing it with anything but an excellent coffee grinder.” He also writes that a basic thermoblock machine, the cheapest kind, can “certainly produce good espresso” when it’s paired with a good grinder.
What Gagné’s analysis of 24 grinders found
One large set of espresso grinder measurements comes from the Kaffeemacher team, who compared 24 espresso grinders. Marco Wellinger at the Zurich University of Applied Sciences (ZHAW) measured the grounds with a Camsizer X2 imaging instrument, using one coffee, an 82-point natural Brazilian, across a range of settings and at each grinder’s dial-in for a ristretto, an espresso and an allongé. Jonathan Gagné, an astrophysicist who studies coffee, analyzed those 300 particle-size distributions and published his findings on his blog in 2023. What he found, each with what it rests on:
- Fines, compared at one size. He measured fines as the share of the coffee’s volume finer than 100 µm. To compare grinders fairly, he read each one’s fines at a median particle size of 340 µm, a point every grinder had measurements on both sides of. It’s a reference point for the comparison, not a size the grinds were set to. It’s also coarser than the Grind Guide’s illustrative espresso band of 200 to 300 µm; Gagné cautions that different instruments report sizes differently, so read it within this data set.
- Dialing in sets the fines. Grinders that made more fines had to be set coarser to reach the same shot, and the most unimodal grinders, those with the fewest fines, needed a much finer average grind. Gagné concludes that when we dial in espresso, we’re setting the amount of fines more than the average size of the coarser particles.
- The low-fines grinders “over-shot”. At dial-in, the more unimodal grinders needed a slightly larger amount of fines per gram than the others, rather than the same amount. He calls this hard to explain and suspects the puck compresses or rearranges under pressure.
- A flow rule from geophysics didn’t fit. A rule used in geophysics predicts flow through a bed from the 10th-percentile particle size, squared. The dialed-in espresso grinds didn’t follow it from grinder to grinder. His candidate explanations, untested, are differences in the early shot’s viscosity, the puck being reshaped by pressure or fines migrating, and unusual particle shapes.
- Shape and size. Conical burrs were less unimodal and less uniform than flat burrs on average, with a large overlap. Within this sample, larger burrs didn’t systematically make more uniform or more unimodal grinds; Gagné suggests tooth geometry and coating may matter more. Our conical vs flat guide has the details.
- Taste. The Kaffeemacher team blind-tasted a subset of the grinders. Their favorites had middle-of-the-road unimodality and uniformity, with the Niche Zero and the Baratza Forté near the top, while a grinder with a similar spread, the G-Iota, rated poorly. Gagné reads that as a sign that something not visible in a particle-size chart, perhaps clumping or heating, also mattered, and says it’s hard to call conclusive.
He lists the limits himself: one coffee, one unit of each grinder so alignment is unknown, and rpm and feed rate not controlled. And he notes that the idea that more uniform burrs give higher extraction “remains to be demonstrated.”
The practical upshot is modest. A better grinder isn’t simply one with the narrowest spread; the measurements show real differences between grinders, but the best-tasting ones weren’t the extremes, and a chart of one unit doesn’t tell you how a particular grinder will taste in your kitchen.
Burr size and sharpness: what Rao reports
Rao is more emphatic. In Espresso Extraction (2013) he writes, “Simply put, bigger burrs are better”: in his account, larger burrs make fewer fines and narrower distributions, damage the flavor less through heat, and dull more slowly. From his experience, he describes large-burr grinders producing delicious espresso at 21 percent extraction, while some small-burr grinders couldn’t make acceptable espresso above 19.5 percent, comparing equally sharp burrs. He calculates that the higher extraction cuts bean cost by about 7 percent.
That’s a practitioner’s experience rather than a measurement across many grinders, and it sits alongside Gagné’s finding that burr size alone didn’t predict uniformity in the 24-grinder set. Both can hold: the burrs’ size, geometry, sharpness and alignment all vary between grinders, and no single one of them settles the question.
On sharpness, Rao writes that sharper burrs make narrower distributions, and that as burrs dull they make more fines and more boulders, with the net result of slower flow and lower extraction. He gives an illustration of how the best extraction drifts down over a burr set’s life, and describes a friend whose careful logging found that each of five changes raised his average extraction by up to 0.5 percentage point, one of them replacing old burrs with a new, sharp set. Hoffmann’s advice on when to replace burrs is to follow the grinder maker’s recommendation.
Blade grinders and static
A blade grinder is the clearest case for upgrading. Hoffmann explains that its blade smashes the beans, making both very fine powder and very large pieces, while a burr grinder can’t release a piece until it has been cut down to the gap between the burrs. Easto’s one-purchase advice is a burr grinder for the same reason.
Static is a smaller, separate issue. A 2024 study in Matter found that a little water on the beans before grinding, the Ross Droplet Technique, reduced the charge on the grounds and broke up clumps; the authors noted that almost no grounds were left in the grinder, but didn’t measure it. Our RDT guide covers the study and what grinder makers say.
Is your grinder the bottleneck?
Upgrade the grinder first if:
- You use a blade grinder, or pre-ground coffee, for espresso. Neither lets you grind fresh and adjust finely.
- You can’t grind fine enough to slow the shot to your recipe’s time, or the steps between settings are too big to fine-tune it. Those are Hoffmann’s two jobs for an espresso grinder.
- The burrs are worn or seated badly. Rao’s sign of dulling burrs is extraction and strength slowly declining over months, with more bitterness and astringency, when nothing else has changed. He also warns that a ground or two trapped under a reseated burr can tilt it enough to hurt the grind. Our burr alignment guide covers how to check.
Look elsewhere first if your grinder does those jobs well:
- Shots that are uneven or vary from one to the next often come from puck preparation. In Gagné’s 2021 study of 24 shots on a Decent DE1, all ground on a Niche Zero, stirring only the top of the bed left the puck’s peak resistance varying by about 40 percent from shot to shot, and stirring to the bottom narrowed it. Our WDT guide and channeling guide cover the fixes.
- The machine can be the limit. Hoffmann writes that thermoblock machines don’t hold a very consistent water temperature and can’t brew and steam at once, and that many owners soon feel constrained by them; dual-boiler machines give finely tuned, stable brew temperatures. Don’t shop by a pump’s quoted 15 bars: he puts the pressure espresso wants at around 9, with a valve releasing the excess.
- The recipe. Rao suggests a dose within about 10 percent of what your basket is designed to hold. Our espresso dial-in guide starts from the Brew Guide’s 18 g in, 36 g out in 25 to 30 seconds.
Whatever you grind with, set it from the maker’s own starting point and adjust by taste.
For choosing one, our espresso grinder guide compares makers’ specifications, and our grind size micron chart explains how grinds are measured.
Sources
- James Hoffmann, The World Atlas of Coffee, 2nd ed. (Octopus/Mitchell Beazley, 2018): pp. 70–71 (blade and burr grinders, grind size in espresso, burr replacement, “investing in a better grinder first”); pp. 110–111 (thermoblock, heat-exchange and dual-boiler machines; espresso grinders; “A word of advice”)
- Jessica Easto, Craft Coffee: A Manual (Agate Surrey, 2017), p. 30 (all grinders make a distribution; buy a burr grinder first), p. 84 and p. 91 (grinder, then scale)
- Jonathan Gagné, “What I learned from analyzing 300 particle size distributions for 24 espresso grinders,” Coffee ad Astra, September 21, 2023 (first published on Patreon, April 29, 2023): the data set, fines at 340 µm, dial-in, over-shooting, the 10th-percentile flow rule, burr shape and size, the blind tastings and the caveats: coffeeadastra.com
- Jonathan Gagné, “A Study of Espresso Puck Resistance and How Puck Preparation Affects it,” Coffee ad Astra, January 16, 2021: coffeeadastra.com
- Scott Rao, Espresso Extraction: Measurement and Mastery (2013): chapter 1, “What Is an Ideal Extraction?” (dose and basket); chapter 9, “Grinding” (particle-size distribution, burr size, burr sharpness, structural grinder problems); chapter 13, “The Benefits of Using a Coffee Refractometer” (burr sharpness trends; the 0.5-point changes)
- J. Méndez Harper et al., “Moisture-controlled triboelectrification during coffee grinding,” Matter 7, no. 1 (2024): 266–283: doi.org/10.1016/j.matt.2023.11.005
- Grind Calibrator entry for the Niche Zero, from Niche’s grind size guide, as cited in the tool