Chemex Coffee Grind: Getting the Perfect Grind Size for Your Chemex

The ideal Chemex coffee grind is medium-coarse, similar to the texture of coarse sea salt. It should be noticeably chunkier than the standard drip grind you'd use in an automatic coffee maker, but not as big as the coarse grind you'd use for French press. Getting this right is probably the single biggest factor in whether your Chemex brews taste clean and sweet or bitter and muddy.

I've been brewing with a Chemex for about three years now, and I spent the first month making terrible coffee with it. The problem was grind size every single time. Once I dialed in the right grind, the Chemex went from frustrating to my favorite brewer. Let me save you that month of trial and error.

Why the Chemex Needs a Specific Grind Size

The Chemex uses thick, bonded paper filters that are 20-30% heavier than standard drip coffee filters. This is the defining feature of the Chemex, and it directly dictates the grind size you need.

These thick filters do two things. First, they remove more oils and fine particles from the coffee, producing an exceptionally clean, bright cup. Second, they slow down the water flow significantly compared to thinner filters. Water takes longer to pass through a Chemex filter than through a V60 filter, for example.

Because the water drains slowly through the thick filter, you need coarser grounds to keep the total brew time in the right range (3.5 to 5 minutes for a standard 30-ounce Chemex batch). If you use a fine or even standard medium grind, the water pools on top of the coffee bed and takes way too long to drain. This over-extracts the coffee and produces a bitter, harsh cup. But, if your grind is too coarse, the water rushes through without extracting enough flavor. You end up with a thin, sour, watery cup that doesn't taste like much of anything.

The sweet spot is medium-coarse: big enough to let water flow at a steady rate through that thick filter, but small enough to extract good flavor in the 4-minute window.

What Medium-Coarse Actually Looks Like

Visual references help more than words here.

Too fine (drip grind): Looks like table salt or regular sand. This will clog your Chemex filter and make a bitter mess.
Just right (medium-coarse): Looks like coarse sea salt or raw sugar crystals. You can see distinct individual particles, and they feel gritty (not smooth) between your fingers.
Too coarse (French press grind): Looks like crushed peppercorns or small gravel. This will under-extract and taste weak in a Chemex.

If you're using a burr grinder with numbered settings, medium-coarse is typically about 60-70% of the way toward the coarsest setting. On a Baratza Encore, that's roughly settings 20-25. On a Timemore C2, about 22-26 clicks. On a 1Zpresso JX, roughly 28-32 clicks. These are starting points, not gospel. Every grinder is calibrated slightly differently.

How to Dial In Your Chemex Grind

The exact grind setting depends on your beans, your water, and even the ambient humidity. Here's the method I use to find the right setting.

Step 1: Start Medium-Coarse

Set your grinder to the middle of the medium-coarse range based on the suggestions above or your grinder's manual.

Step 2: Brew and Time It

Use a standard recipe to start: 42 grams of coffee, 680 grams of water (about 24 ounces), water at 200-205F. Pour slowly in circles, starting with a 60-gram bloom pour, waiting 45 seconds, then pouring the rest in stages.

Time the entire brew from the first pour to the last drop through the filter.

Step 3: Evaluate

Brew finished in under 3.5 minutes: Your grind is too coarse. Go 1-2 settings finer.
Brew finished in 3.5-5 minutes: You're in the right ballpark. Taste the coffee.
Brew took longer than 5 minutes: Your grind is too fine. Go 1-2 settings coarser.

Step 4: Taste and Adjust

Even if the timing is right, your taste buds have the final say.

Coffee tastes sour, thin, or tea-like: Go finer. The water isn't extracting enough.
Coffee tastes bitter, dry, or ashy: Go coarser. The water is pulling too many harsh compounds.
Coffee tastes sweet, clean, and complex: You found it. Write down your grinder setting and this specific bean so you can return to it.

I recommend making one adjustment at a time. Change the grind by just one setting, brew again, and compare. Jumping multiple settings makes it harder to isolate what changed.

The Grinder Makes or Breaks Your Chemex

The Chemex is particularly sensitive to grind consistency because of how the thick filter interacts with the coffee bed.

In a well-ground dose, all the particles are roughly the same size. Water flows through evenly, extracting each particle the same amount. The result is a balanced, clean cup.

With inconsistent grounds (lots of fine particles mixed with large chunks), the fine particles migrate to the bottom of the filter and form a dense layer. This layer acts like a dam, dramatically slowing drainage. Meanwhile, the coarse particles at the top under-extract. You get the worst of both worlds: the fines over-extract (bitterness) while the coarse pieces under-extract (sourness).

This is why blade grinders are a poor match for Chemex brewing. The random particle size distribution creates exactly this problem. A burr grinder, whether electric or hand-operated, produces much more uniform particles and gives you consistent results.

If you're looking for grinder recommendations specifically for Chemex brewing, our best coffee grinder for Chemex guide covers the top options at every price point.

Bean Type and Roast Level Adjustments

Different coffees need slightly different grind settings even in the same Chemex.

Light roasts are denser and harder. They resist grinding and tend to produce slightly coarser particles at the same grinder setting compared to darker roasts. They also extract more slowly. For light roasts, I typically grind 1-2 settings finer than my default and use water at 205F (the upper end of the range) to help with extraction.

Medium roasts are the easiest to work with in a Chemex. They extract predictably and taste great at the standard medium-coarse setting. If you're new to Chemex brewing, start with a medium roast while you learn the technique.

Dark roasts are more porous and brittle. They shatter into finer particles more easily and extract faster. For dark roasts, go 1-2 settings coarser than your default and use slightly cooler water (195-200F) to prevent over-extraction. Dark roasts can turn bitter fast in a Chemex if you're not careful.

Single origins often have more distinct and delicate flavors that the Chemex shows off beautifully. The clean cup profile lets you taste specific tasting notes (fruity, floral, nutty) more clearly than many other brewers.

Blends work fine in a Chemex but tend to taste more generically "coffee-like" since the component flavors blend together rather than standing out individually.

Common Chemex Grind Mistakes

I've made all of these. Learn from my errors.

Using pre-ground "drip" coffee. Pre-ground coffee from the store is ground for auto-drip machines, which use thinner filters. It's too fine for Chemex. Your brew will take 7+ minutes, taste bitter, and the filter might even overflow. Always grind fresh and grind medium-coarse.

Not adjusting for dose size. If you're making a smaller Chemex (3 cups instead of 6), you might need to adjust slightly coarser. A thinner bed of coffee drains faster, so a slightly coarser grind keeps the timing in range. Conversely, a large batch with a deep coffee bed might need a slightly coarser grind too, to prevent clogging.

Ignoring filter fold direction. This isn't a grind issue exactly, but it affects drainage. The Chemex filter should be folded with the three-layer side against the pour spout. This creates a small air channel that lets air escape as water drains. If you block the spout, the vacuum effect slows drainage dramatically, making your perfectly ground coffee taste over-extracted.

Grinding too far ahead. Grinding the night before for your morning Chemex is tempting, but the flavor degradation is real. Even 8 hours of exposure causes noticeable loss of aromatics. Grind right before you brew.

For a full overview of grinders suited to all brew methods including Chemex, see our best coffee grinder guide.

FAQ

Can I use the same grind for Chemex and V60?

No, they need different grinds. The V60 uses much thinner filters and has a larger drain hole, so it needs a finer grind (medium to medium-fine) to slow down the flow rate enough for proper extraction. Using a Chemex grind (medium-coarse) in a V60 will produce under-extracted, watery coffee. If you use both brewers, you'll need to adjust your grinder between them.

Why does my Chemex coffee taste watery?

The most common cause is too coarse a grind. If the water passes through the coffee bed too quickly, it doesn't extract enough soluble flavor compounds. Try going 2-3 settings finer on your grinder. Also check your coffee-to-water ratio. If you're using less than 42 grams of coffee per 680 grams of water (a 1:16 ratio), your brew will taste diluted regardless of grind size.

Should I bloom the coffee in a Chemex?

Yes. Blooming means pouring a small amount of hot water (about 2x the coffee weight, so 80-90 grams for a 42-gram dose) over the grounds and waiting 30-45 seconds. This releases trapped CO2 from freshly roasted beans. If you skip the bloom, the CO2 creates bubbles in the coffee bed that disrupt even water flow. Blooming gives you a more even extraction and a cleaner cup.

How many cups does one Chemex brew make?

A standard 6-cup Chemex actually makes about 30 ounces of coffee, which is closer to 3-4 normal mugs. The Chemex "cup" measurement uses a 5-ounce cup, which is smaller than what most people drink. For one person, a 3-cup Chemex (about 15 ounces) is usually enough for a generous mug with some left over.

Start Here

Get a bag of medium-roast beans from a local roaster, set your burr grinder to medium-coarse, and follow the 42g/680g recipe above. Time your brew. Taste your coffee. Make one small adjustment. Repeat until you hit that sweet spot where the coffee tastes clean, sweet, and complex. Once you find it, the Chemex rewards you with some of the most elegant coffee you can make at home.