If you’ve ever opened a fresh bag of coffee beans and used your grinder in the usual way only to have the coffee turn out flat and tasteless, you’re not alone! What’s at fault is not your water or your grinding technique. What’s to blame most often is the grind size.
In this post, we explain precisely how roast level affects the structure of coffee beans, and why you need to change your manual coffee grinder grind size to accommodate that change. We explain how light, medium, and dark roasts impact the beans, and how you should subsequently change the dial on your manual coffee grinder grind size to make the most of the pot you’re about to brew. We also offer a step-by-step guide to help you achieve the perfect manual coffee grinder grind size!
Why Roast Level Affects Grind Size: The Bean Science
Think about what happens to coffee beans when they come into contact with a roaster. As the heat of the roasting process increases, the beans’ cells start to break down. The hotter the process, and the longer it takes, the more damage is done to the beans’ cells.
This damage is not merely cosmetic. It determines just how hard your grinding mechanism has to work, how evenly the beans break apart during grinding, and how quickly water extracts the flavours you need for a delicious pot of coffee.
Now let’s look at the impact of different roast levels.
- Light roast
The scientific factor: When the beans are roasted for less time, they are left with more of their original structure. The beans remain dense, hard, and more or less intact. When you add hot water (in a French press, for example) the coffee is extracted more slowly than it is with other roast levels.
Your grind solution: Finer grind is the right choice for your manual coffee grinder grind size. Light roast allows for more time for the grounds to produce deep, floral flavours.
- Medium roast
The scientific factor: The beans’ cell walls expand with heat, leaving them partially broken. This leaves the beans’ structure somewhat brittle. Water can therefore pass through these pieces at a steady, even rate.
Your grind solution: To get the best flavour from medium roast, choose the standard setting for your manual coffee grinder grind size.
- Dark roast
The scientific factor: The longer beans are roasted, the more their cells collapse. This leaves them with a sponge-like construction, through which water pours easily and thus causes fast extraction.
Your grind solution: A coarser grind is best for dark roast coffee. Larger pieces slow down the brewing process, which prevents bitterness. That’s why, when you opt for dark roast, it’s best to set your manual coffee grinder grind size to coarse.
Best Grind Size for Light Roast Coffee
Light roast coffee beans are, in fact, very dense. Their unsullied cells mean that the flavours are bright, floral, and aromatic. Because the beans have not been broken down during the roasting process, water has to work extra hard to extract those flavours.
Placing your manual coffee grinder grind size to a standard setting won’t allow those tastes to be fully extracted. The coffee will, in all likelihood, taste thin and watery. You can avoid that by setting your manual coffee grinder grind size to a quite fine setting. Doing so allows the water to access the grounds more fully.
On most manual grinders, switching your grind from medium to a finer setting – two or three more clicks, usually – for light roast beans does the trick. Grind size is the most important factor when it comes to getting the fullest flavour from light roast beans.
Light roasts also benefit from slightly hotter water (93–96°C / 199–205°F) because higher temperatures help break down the cell walls and speed extraction. But grind size is the primary lever — get that right first.
Best Grind Size for Medium Roast Coffee
Using medium roast coffee beans is where most home coffee makers master the art of grind size. That’s because medium roast has been through the process just long enough to offer rich, deep, and slightly caramelized tastes, which are incredibly popular with coffee drinkers. Medium roast beans are ideal for brewing almost any kind of coffee, whether it’s your morning cup or an after-dinner espresso. Even novice coffee makers can make a great cup with medium roast beans, because their size allows for a wide range of grind options. Using medium roast beans gives you reliably delicious grounds when you use your manual coffee grinder.
For pour-over coffee, a medium roast usually demands a medium-fine grind, while making espresso requires a fine grind. If you’re using a French press, a medium-coarse grind is ideal. These are the best settings that coffee manufacturers suggest. If your manual coffee grinder came with a grind size chart, by all means follow it!
One thing to bear in mind with medium roast beans is how wide the range of uses is for this level. There is quite a difference between a light to medium roast and a light roast, so read your manual grinder’s chart carefully. There is also a big difference between medium and medium dark – even a small change in your manual coffee grinder grind size setting can cause a big change in flavour! Start by reading the label on the beans, then consult more information before you grind.
Best Grind Size for Dark Roast Coffee
Dark roast beans are porous and even brittle, which means they have virtually no resistance to water. Coffee extraction happens quickly, occasionally too quickly! If you grind dark roast coffee too fine, water simply rushes through and squelches the chocolatey notes you want. This rushing may also leave the coffee with an acrid, bitter flavour, which you definitely don’t want.
Dark roasts demand a coarse grind, not a fine one. A coarser grind slows down the extraction process. The slowness gives you more control, which means the coffee flavours stay rich and sweet without ever becoming bitter.
Dark roasts produce fine particles (known as fines) when you grind because the brittle beans shatter easily under burrs. These little particles may clog your grinder, so be sure you clean it before changing the setting to a different one.
How to Adjust Your Manual Coffee Grinder for Every Roast Level
There is one advantage to manual coffee grinders that’s particularly significant – they are reliable even after repeated uses. Every use puts your burr into a precise spot, which lets you know exactly what grind size you prefer for every type of coffee you brew. Here’s a guide to creating your flow chart:
First of all, read the back of your bag of beans. Take note of the roast level and the date. If it’s a lighter roast, plan to grind it on the finer side.
Secondly, make note of your brewing method. If you’re using a pour-over method, like a Melita, you’re usually going to use a medium to coarse grind. For espresso coffee, you’ll want a grind set to medium-fine. If you’re using a French press, turn the grinder two or three clicks, depending on the roast level.
Brew a pot and be critical about the outcome. Is it rich and deep? Is it too watery? If it’s the latter, that means that your grind likely needs to be finer. If it’s too strong, bitter or unpalatable, grind it more coarsely. Once your cup of coffee is delicious and well-balanced, you know you’ve set your manual coffee grinder grind size to the perfect spot!
Make changes one at a time. If the coffee doesn’t satisfy you, don’t change everything all at once. Consider buying different beans, or do more research on roast levels, or alter the grind setting – but don’t do these all at once! Figure out slowly what needs to change by altering each aspect until you’re sure of what the issue is.
Track your settings. Take note of everything from grind size to water temperature, brew time, and measurements. The next time you brew a pot of coffee, you’ll be glad you’ve got all this info.
Manual Burr Grinder vs Blade Grinder: Why It Matters for Roast-Based Dialing
None of what we just explained is possible with a blade grinder! Blade grinders simply chop up beans in a random fashion, which produces randomly sized grounds. Some turn out powdery, some coarse. Consequently, you can’t control the grinder’s output, which in turn means you can’t adjust because of the roast level. Every bag of beans is a roll of the dice!
A manual burr grinder is a different story, whether it’s a conical or flat burr grinder. These grinders crush beans between two surfaces that are evenly spaced. Consequently, the bits are sized consistently. When every bit of the grounds is uniformly sized, the result is a perfect grind, over and over again. Even a small change to your manual coffee grinder grind size, therefore, makes a welcome and predictable change in the coffee you’re brewing.
Grind Size and Roast Level FAQ
- Does the roast level make grinding harder?
Well, yes. Because light roast beans are denser and tougher to break, they demand more effort with each turn. Dark roast beans, as we discussed, are more brittle, and therefore, they grind more quickly and easily. If your arm is fatigued after grinding light roast beans, that’s natural! It’s not a signal that something’s wrong with your grinder.
- Should I turn the knob between roast levels? If so, how much?
Here’s a helpful starting point: turn the knob just slightly finer for light roasts, and turn it to slightly coarser for dark roasts. Every manual grinder is unique, and therefore, there is no one universal rule for all of them. Just remember: what a small turn engenders on one grinder may have a different result on another type. Once you find the best setting for your manual coffee grinder’s grind size for a rich, delicious brew, you’ll know where to keep it set for the next time.
- Is the same grind size okay for all roast levels?
You can leave your grinder on one setting, but it may result in less-than-fabulous coffee. To get the most from your manual coffee grinder, adjust it when you change roast levels.
- Which manual grinder is best for adjusting the roast level?
Check the grinder for a numbered adjustment dial on conical or flat burrs – remember, don’t buy a blade burr! Quality kitchen tools manufacturers like Holar build their grinders to precise industry specs, so keep these companies in mind when you’re shopping. The best manual coffee grinder isn’t always the most expensive. The best is one that gives you a consistently reliable grind size every time.
- Which is more important, grind size or water temperature?
Both matter, but grind size has the larger impact on extraction in most manual brewing methods. It’s the first dial to reach for when a cup tastes off.
Key Takeaways
Roast level and grind size work together. Each bag of beans you buy is destined to give you a great – or mediocre – pot of coffee because of the roast level. But your manual coffee grinder grind size has a huge impact, too.
Light roasts require a finer grind to release the coffee’s taste and aroma held within the beans. Dark roast demands a coarser setting to make the most of its flavours. Medium roasts lie somewhere in the middle, offering you a steady baseline against which you can assess other settings. Set your grind dial according to the roast, then assess the coffee you’ve brewed with a critical eye. The adjustments you make to your manual coffee grinder’s grind size will make the difference between a mediocre pot of coffee and a memorable one!
