Which Grinder / Glossary
Coffee grinder terms explained
27 words you meet in grinder reviews, in plain English. Each one says what it is, why it matters and, when there is a better direction, which way it is. On a grinder page, tap a dotted word for the short version.
Grind quality
What comes out of the grinder, and how even it is.
Retention
Lower is better
Retention is the ground coffee that stays inside the grinder after you finish, usually measured in grams. It matters because old grounds can mix into your next dose, and because you lose some of the beans you weighed. It matters most if you switch beans often or weigh every dose.
Grind variation (uniformity)
Lower is better
A grinder never makes particles of exactly one size. Grind variation, also called uniformity, describes how widely the sizes spread around the size you aimed for. A more even grind tends to extract more evenly, which many people taste as a cleaner cup.
Fines
Lower is better
Fines are the tiny dust-like particles that every grinder makes next to its target grind size. They extract quickly, so many of them can add bitterness or make the cup muddy, especially in filter coffee. Some fines are normal, and espresso copes with them better than filter coffee does.
Boulders
Lower is better
Boulders are particles that are much bigger than the grind size you aimed for. They extract slowly and can leave a thin or sour taste next to the finer particles. A grinder that makes fewer boulders gives a more even cup.
Microns (µm)
A micron, written µm, is one thousandth of a millimetre. Reviewers use it to describe how fine a grind is and how far one click or step moves the burrs. A smaller number means a finer grind, or a smaller step.
Dose consistency
Lower is better
Some electric grinders grind for a set time, so each dose can weigh a little differently. Reviewers report this as a standard deviation in grams, which is how far doses typically stray from the average. Lower is better, because each dose then lands closer to the weight you want.
Workflow
How a grinder behaves day to day, and which brew methods it suits.
Single dosing
Single dosing means you weigh just the beans for one brew, grind them, and keep the rest sealed. It keeps old beans out of the grinder and makes it easy to switch coffees. It works best on grinders with low retention, because leftover grounds matter more when you grind small amounts.
Grind speed (g/s)
Higher is better
Grind speed tells you how long a dose takes. Reviewers give it in grams per second, or as the seconds needed for a set dose such as 18 g. A higher figure in grams per second means a faster grinder, and fewer seconds per dose means the same. It matters most for filter batches, and for hand grinders where you do the cranking.
Popcorning
Lower is better
Popcorning happens when beans jump around in the hopper or bounce off the burrs instead of dropping in steadily. It is most common with a small amount of beans, such as when single dosing, and it can slow the grind or leave beans behind. Less popcorning is better, and a lid or a hopper shape that holds the beans down can help.
Static
Lower is better
Static is an electric charge that builds up as beans are ground, so grounds stick to the container and scatter over the counter. It tends to be worse with dry beans and dry air. Less static means less mess and less lost coffee, and many people add a tiny spritz of water to the beans before grinding to calm it.
Turkish
Turkish coffee is brewed in a small pot called a cezve, and it needs a grind as fine as powder, finer than espresso. Many grinders cannot go that fine. We mark Turkish as a brew method only when a maker or a reviewer says the grinder can do it.
Filter machine
A filter machine is an automatic drip or batch coffee maker, such as a Moccamaster. It takes a medium grind, similar to pour-over, so we follow the pour-over rating. A pot needs a lot of coffee at once, so a grinder with a small bean container or slow output can be a poor match, and we mark that as limited.
Mechanics
The parts inside the grinder and how you set it.
Burrs
Burrs are a pair of toothed metal discs or cones that crush coffee beans into pieces. The gap between them sets the grind size, and their shape, size and sharpness affect speed, evenness and taste. Burr grinders are generally preferred over blade grinders because they crush beans to a more even size.
Burr size (mm)
Burr size is the width of the burrs, given in millimetres. Bigger burrs generally grind faster, because there is more cutting surface. A bigger burr does not make better coffee by itself, because the burr shape and how well it is made matter as much.
Flat burr
Flat burrs are two flat, toothed rings that face each other, with the beans passing between them. They are often said to give clearer, more distinct flavours, while conical burrs are said to give a rounder cup. The difference is small and depends on the grinder more than on the shape alone.
Conical burr
A conical burr set has a cone-shaped burr that turns inside a ring-shaped one. It is common in hand grinders, because it turns easily and can be compact, and in many home electric grinders. Conical burrs are often said to give a rounder cup than flat burrs, though the difference is small.
Steps and stepless adjustment
Adjustment is how you set the grind size. A stepped grinder clicks between fixed settings, which makes it easy to return to a setting. A stepless grinder turns smoothly to any point, which gives finer control, especially for espresso where tiny changes matter. Smaller steps also give finer control, so a stepped grinder with small steps can feel almost stepless.
RPM
RPM stands for revolutions per minute, which is how fast the burrs spin. A higher RPM can grind faster, but it can also be louder and warm the grounds more, so neither a high nor a low RPM is better by itself. Hand grinders turn at the speed of your hand, and electric ones list a motor speed.
Burr alignment
Burr alignment is how squarely the two burrs face each other as they turn. If one wobbles or tilts, some beans are crushed unevenly and the grind gets less even. Well aligned burrs are better, and a stiff, well made grinder tends to keep its alignment for longer.
Burr seasoning
Seasoning means grinding through some beans, often cheap ones, so new burrs wear in. Owners and reviewers often report that new burrs behave a little differently at first, for example with more retention, and that this settles with use. So a reading taken on a brand new grinder can differ a little from one taken after months of use.
Noise
How loud a grinder is, and how we show it.
dB (decibels)
Lower is better
A decibel, written dB, measures how loud a sound is. A lower number is quieter, and every extra 10 dB sounds roughly twice as loud. Readings depend on the microphone distance and the room, so compare numbers from one tester more than numbers from different testers.
Noise levels 1 to 5
Lower is better
Our noise level is a scale from 1 to 5. Level 1 is a hand grinder, which has no motor, and level 5 is very loud. The level follows from a published dB reading, or from what several reviewers say, and the page names its source. A lower level is quieter.
Buying
Prices, ratings and the labels we use on grinder pages.
Delivered price
Lower is better
The delivered price is the total you pay to get the grinder to your door. It is the shop price with the VAT of your country where the shop charges it, plus shipping. Two shops can have the same shelf price and still differ a lot once shipping and VAT are added, so we compare the delivered price.
VAT
VAT, short for value-added tax, is the sales tax on goods in the EU, and its rate differs by country. Many shops charge the VAT of the buyer's country on orders sent across a border, so the same grinder can cost a different amount in each country. Our prices include VAT, so the price you see is what you pay before shipping.
Reviewer consensus
Reviewer consensus counts how many independent reviewers who wrote about a model recommend it. We show each reviewer's own score beside its source. We never average the scores into a single number of ours, because reviewers use different scales and methods.
Owner rating
Higher is better
An owner rating is the average score that buyers gave one exact grinder on a shop's own product page. We show it only when at least 20 people rated it, and we leave out ratings that belong to a company or to another model. A higher rating is better, but a rating from a few people says little.
Limited fit
A grinder marked limited for a brew method can do it, but that is not what it does best. Typical reasons are steps that are too coarse for fine adjustment, a missing upgrade, or owners who report that it struggles. A yes means it handles the method well, and a no means it cannot reach it.
These are the terms our grinder pages use. How we research explains how we rate brew methods, noise and prices.