Conical vs Flat Burr Grinders: Is There a Clear Winner?

Oh, boy. I’ve been dreading writing this article about conical vs flat burr grinders. It’s such a touchy subject that I know choosing a definitive “best” burr type is going to earn me some haters.

So, I’m not going to choose. I’ll say it here and now: I love burr grinders. All of them! No matter what their burrs look like.

Still, this article is a long time coming. I’ve touched on the conical vs flat burr debate several times over the years, so I figured it was time to take a closer look.

In this article I’m going to explore the nitty-gritty of conical vs flat burrs. And while I won’t pick my favorite, I will let you know the advantages and disadvantages of each burr type so you can decide for yourself.

Besides, having the know-how to engage in a spirited coffee debate is part of the fun of our global coffee community! Let’s get into it.

Wait, What About Blade Grinders? 

You’ll notice that I’m not writing a conical vs flat burr vs blade grinder article here. I’ve said it a million times already, but I’ll reiterate for good measure: blade grinders are ruining your coffee.

Blade grinders haphazardly chop up coffee beans with cheap metal blades. In other words, it’s impossible to achieve consistency or precision when grinding coffee with a blade grinder.

So if you haven’t already, make the switch to a quality burr grinder! After all, consistency and precision are essential to brewing exceptional coffee.

Now that I’ve gotten that out of the way, I can focus on the real questions at hand. Read on below!

What Are Conical and Flat Burr Grinders?

If I’m going to dip my toe into the conical vs flat burr debate, I first need to make sure we’re all on the same page. So, what are flat and conical burrs?

In short, burrs are sharp cutting surfaces that chop coffee beans into small pieces. In both flat and conical burr grinders, one burr remains stationary while the other spins against it. Coffee beans get smaller as they pass between the two sharp burrs. And the distance between the burrs determines the resulting grind size.

Those are the similarities between flat and conical burrs, so what about the differences?

Conical burr grinders feature one conical, or cone-shaped, burr which sits inside of a ring-shaped burr. Conical burrs have sharp grooves that feed the coffee beans into the grinds chamber.

Meanwhile, a flat burr grinder has two flat burrs that are parallel to one another, with the sharp sides facing. These flat burrs have sharp teeth that chop the coffee into small pieces before pushing them into the grinds chamber.

As far as materials go, conical burrs can be either ceramic or stainless steel. And while flat burrs are often made of steel, they are sometimes ceramic.

Incidentally, a burr grinder with conical burrs relies on gravity to push grounds out. In other words, coffee beans are loaded into a hopper (or just dropped on top of the burrs, in the case of a manual grinder), then pass through the burrs and exit into the grinds chamber below.

Conversely, the construction of a flat burr grinder often has the grind chute beside the burrs instead of below them. As a result, burr grinders often have higher RPM, since the motor needs to work harder and the burrs need to spin faster to push the coffee grinds out.

Does Burr Shape Affect Coffee Quality?

This is one of the touchiest questions in the coffee world. While some coffee experts will vehemently argue that one burr shape results in superior cup quality, I disagree.

After all, the shape of the burrs isn’t the only consideration. The speed and power of the motor, build quality, particular burr geometry and other factors all work together to produce the coffee grinds.

However, while I don’t believe that burr shape can affect coffee quality, I do think that it can influence the specificqualities and flavor notes in a cup of joe.

Take these observations with a grain of salt. I haven’t done thorough testing on this subject, and I’m wary of generalizations even if I do have experiments to back up my opinions.

Still, during my years as a coffee professional I have noticed a couple of trends.

Flat burrs often provide more clarity in a cup profile. Meanwhile, conical burrs often produce a rounder mouthfeel and full body. Many espresso machines come with integrated burr grinders. A great example of a machine featuring a built-in conical burr grinder is the Ninja Luxe Cafe. In contrast, the Gaggia Brera features a a flat burr grinder.

That said, this is not always true. The specific burr geometry of different models can produce wildly different cup profiles, even within the category of each burr type.

What’s more, manufacturers of flat and conical burr grinders are consistently working to improve burr performance. With today’s advanced technology, conical burrs can produce a clear cup while flat burrs can produce a rounder cup. Go figure, right!?

Conical vs Flat Burr Grinder: Which Is Better?

Again, I can’t give you a clear answer here.

If you read my guide to choosing the best burr grinder, you’ll see that I highlight a few different factors to consider. These include the size of the grinder, its overall build/design, materials used, your budget and your intended brewing method.

The same factors go into deciding between a conical or flat burr grinder.

Most of those factors are tied to a grinder’s specific model and manufacturer. That said, I can speak more generally about the budget differences between conical burrs and flat burrs. 

As a general rule, flat burr coffee grinders are more expensive than conical burr grinders. They require a bigger and stronger motor, which means the coffee grinder itself must be bigger. So, this inevitably drives up the cost.

Of course, other factors contribute to the price of a coffee grinder, so this general rule isn’t always true. For this reason (and many other reasons), I don’t think a grinder’s burr shape should be the biggest deciding factor when choosing a burr grinder.

However, if you’re really committed to adding a coffee grinder’s burr shape into your buying decisions, there are a few additional factors to consider:

Grind Consistency

Grind consistency is a super important factor in the ultimate quality of your cup. This is true both for espresso shots and drip methods like pour over.

An inconsistent grind will lead to an unsavory mix of under extracted and over extracted flavors in the cup. Bigger grinds, or boulders, will take longer to extract and could cause channeling. Meanwhile, smaller grinds, or fines, will extract very quickly and could clog a paper filter.

In order to avoid these brewing pitfalls, you’ll want a grinder that can achieve a consistent grind size.

Flat burrs tend to be more consistent than conical burrs. This is due to the design of the burrs and the overall mechanics of flat burr grinders. These factors work together to encourage the burrs to remain parallel, which helps with consistency.

If you want the scientific version, here goes:

Flat burrs have a unimodal distribution, which means that if you analyze the grinds under a microscope you’ll notice that they are all roughly the same size. In other words, a flat burr grinder can produce a very consistent grind.

On the other hand, conical burrs are more likely to have a bimodal distribution, meaning that a large portion of the coffee grinds are one size (boulders), while another large portion are a different size (fines).

This isn’t to say that conical burrs can’t achieve superb grind consistency. They can! But if you look at the graphs, this pattern will be clear.

Noise and Retention

The noise and grind retention of a grinder is more tied to its motor than its burrs. However, as I mentioned before, the type of burr a grinder has does correlate with the motor it requires.

Flat burrs need a bigger and stronger motor that allows them to grind at higher RPM. For this reason, a flat burr grinder is louder than a grinder with conical burrs.

Incidentally, flat burrs also tend to have higher grind retention than conical burrs due to this higher RPM. Electric grinders produce static electricity when they’re on. The higher the RPM, the more static electricity. The static causes grinds to stick to the burrs, meaning a higher risk of grind retention.

That said, in recent years manufacturers have begun tweaking their design to prevent or reduce static and retention. For example, one of my picks for the best espresso grinder, the MiiCoffee DF64 II, features flat burrs and a Plasma Generator to reduce static.

The same goes for the noise issue. Excessive noise can be a problem in both home and commercial environments, so manufacturers are developing techniques to make their grinders quieter.

In fact, I wouldn’t be surprised if, a few years from now, noise and retention is no longer an issue in any quality burr grinder.

Taste

As I mentioned, it’s difficult to make generalizations about how burr shape affects the flavor profile in a cup of coffee. You’d need to do rigorous testing to determine common trends and isolate the effects of the burr shape from other factors, like burr geometry and motor speed.

Still, many serious coffee drinkers do notice some general differences between conical and flat burrs.

Conical burrs often produce a full body with a round flavor profile. Of course, this all depends on the kind of coffee beans you are grinding. Brewing a tea-like coffee such as Panama Geisha likely won’t result in a super full body, even if you do have a conical burr grinder.

On the other hand, flat burrs often lead to a clean and clear cup. This may be due to the superior grind consistency of flat burrs, with less likelihood that fines will muddy your cup.

Naturally, there’s variation among different flat burrs, largely due to manufacturer-specific burr geometry.

Some coffee professionals swear by SSP burrs for espresso and even drip coffee. These are high quality, coated steel burrs that you can buy to replace the standard set that came in your grinder. SSP burrs can produce a cup profile with an even higher clarity and pronounced acidity.

Conical vs Flat Burr Grinders: Advantages and Disadvantages

To help you best decide between conical and flat burrs, I’ve decided to present the advantages and disadvantages of each type.

Flat Burrs

Conical Burrs

Final Thoughts

I hope this article has given you some more insight into the nuances of the flat vs conical burr debate. Plus, if this introduction has intrigued you, I encourage you to read more about this subject and ask your local coffee professionals about their thoughts.

If you have the time and materials, you can even test these different burr types out for yourself!

Whether you’re using an espresso machine or a drip coffee maker, both conical and flat burrs will serve up aromatic, ready-to-brew coffee powder.

Of course, you could avoid this whole debate by just getting a coffee maker with grinder, but where’s the fun in that?

Conical vs Flat Burr Grinders FAQ