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The amount of coffee and water used is an important part of any coffee-brewing process, for the ratio of coffee to water directly impacts extraction. While there are general guidelines that work across most brewing methods, the best extraction comes when the coffee-to-water ratio is specifically adapted for a particular brewing process so that the other variables involved in the process are accounted for. Here’s a guide on how to adapt your coffee-to-water ratio when you’re brewing with a Chemex coffee maker.

General Ratios Range from 1:16 to 1:18

In general, the coffee-to-water ratio used when brewing should be between 1:16 and 1:18. This means that for each gram of coffee used, between 16 and 18 grams (milliliters) of water are used.

Conversely stated, for every 250 grams of water used, you should use between 15.6 and 13.8 grams of water. This conveniently works out to 0.5 ounces of coffee for every 8-fluid-ounce cup of water in the imperial system.

These ratios use weight, rather than volume, because measuring out coffee and water by weight is more accurate. The density of coffee beans can vary, which can lead to using different amounts of coffee when measuring it by volume. Measuring by weight instead avoids this problem, as it accounts for variances in coffee beans’ densities.

A Good Ratio for the Chemex is 1:16.66

While this general range of 1:16 to 1:18 will produce decent brews across most of the brewing spectrum, each particular brew method calls for a more specific ratio within this range. Adjusting the exact ratio used compensates for the other factors that affect extraction, which vary from one brew method to another.

When brewing with the Chemex, the exact ratio that we at Driftaway Coffee recommend is 1:16.66. This is on the lower end of the general range, which reduces extraction. As less water is used, fewer molecules are extracted from the coffee beans.

The Chemex’s filter makes it particularly important to keep extraction relatively low. The filter is thick for a coffee filter, which slows the drip rate of the water and increases the brew time. The increased brew time itself leads to higher extraction. If not checked by adjusting other variables, the resulting brew can become too extracted and quite bitter.

Thus, using a lower coffee-to-water ratio balances out the increased brew time that’s caused by the thicker filter. Using less water not only itself reduces extraction, but it also maintains a reasonable brew time (usually around 7 minutes).

A Ratio of 1:16.66 Also Produces More Body

As an added benefit, using a ratio of 1:16.66 also enhances the body of the final cup. This is a side benefit, but it’s one that’s particularly appreciated by people who transition to the Chemex from a French press.

Enhancing the body by reducing how much water is used helps create a brew that has a body closer to that of a French press’ brew — while still keeping the fines that can lead to bitterness out of the final cup.

Use Fresh Coffee for Best Results

You’ll notice the differences that ratios make when brewing best if you’re using freshly roasted coffee that’s full of flavor. If you don’t already have such coffee, try one of our subscriptions. We’ll send you freshly roasted coffee when you need it.


Author Scott

Scott is a professional writer for Driftaway Coffee. He worked as a barista for eight years, but today prefers to enjoy his beverages from the other side of the counter. When not drinking Driftaway Coffee, Scott usually has a mug of his own roasted coffee nearby.

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