Best Chemex Coffee Ratio:
The Perfect Balance of Coffee to Water

Nail your Chemex coffee ratio with our super simple calculator ensuring you get the most delicious coffee every time.

With an iconic, beautiful design and the ability to make sediment-free, flavorful coffee it’s easy to see why the Chemex coffee maker is wildly popular with coffee fans worldwide. Throw in the very affordable price and it’s hard to say no. 

Getting the brewing process right is obviously key to any great coffee, and Chemex is no different. Whether you’re a noob or a coffee expert, with the help of our calculator you will have the perfect Chemex coffee-to-water ratio. Combine it with our quick brewing guide and you will soon be sipping on the best-tasting coffee possible. 

To make the perfect Chemex coffee, it’s a good starting place to listen to the masters themselves: Chemex.

They recommend starting with 1:15 ratio and, from there, you can adjust to make it stronger or weaker depending on personal preference. We drink strong coffee (a remnant of our days in the service industry), so we prefer to use a 1:12 ratio.

Don’t worry if maths isn’t your strong point, making great-tasting coffee still can be! All this means is that for every 1 gram of coffee, you need 15 ml of water. Working in grams and millimeters gives you a more precise measurement. But, as a rule of thumb, 1 tbsp is the equivalent of 6 gram coffee.

1. Insert & Rinse Your Coffee Filter

Start by opening up a Chemex filter into a cone where one ‘side’ has 3 layers. Place the cone into the top of the Chemex with the 3-layer side covering the spout.

Rinse the filter with some hot water, making sure to cover the whole cone. This removes any unpleasant flavor residue from the filter and pre-heats your Chemex too.

Pour out the hot water ensuring the filter is stuck to the sides of the funnel.

2. Grind and Add Your Coffee

To make the most flavorful coffee, ditch the pre-ground stuff. Pour over really shines when you use freshly ground whole coffee beans as they still have all their delicious flavor-filled oils. There are some pretty cheap but good-quality manual coffee grinders out there so you don’t need to break the bank or add a bulky machine to make good Chemex coffee.

When grinding, you are looking for a medium to coarse grind size, ideally about as coarse as sea salt. As Chemex is one of the most popular coffee methods, your grinder’s manual should be able to guide you as to its best settings.

Using a coffee scale, weigh and add your freshly ground coffee using your ideal Chemex coffee ratio – 1:15 being a good starting point. For best extraction, you want a flat, even coffee bed.

3. Place your Chemex on a Scale

The most accurate way to measure the amount of water you’ve poured is to weigh it as you pour. Place your Chemex, complete with filter and ground coffee, on a coffee scale and press “tare”.

This will reset the scale to zero and you can then weigh out the water you use for perfect accuracy.

4. Bloom the Grounds

Heat the water to around 90°C/200°F. If you can, use a temperature-controlled kettle or thermometer but if you don’t have these things you can bring the water to a boil and then leave off the heat for 2 minutes.

You need to let the grounds “bloom” – fancy coffee speak for releasing the gases from the ground coffee. It’s the first step in coffee extraction as these gases can inhibit flavor extraction from your beans so this step will ensure you get a far better-tasting coffee.

Gently pour a small amount of water over all the grounds in a spiral motion – just enough to wet them. Wait 30 seconds and you’ll see foam developing on the surface. This is called “blooming”.

5. First Pour

After the grounds have bloomed, pour around half of the water over the grounds.

Use a spiral motion to evenly cover the ground coffee and make sure the water stays at least ¼ inch below the top of the Chemex. This is where using a gooseneck kettle really comes into its own as it gives you far better control over the speed of the pour.

6. Finish the Pour

Pour the other half of your water over the ground coffee, continuing in a spiral pattern and making sure they are as evenly covered as possible. You want to keep the funnel at least ¼ full of water and the whole process should take around 4 minutes.

If it takes much longer than this, there may be too many coffee fines restricting the flow rate meaning you need to go slightly coarser with your grind size.

7. Remove the Filter & Enjoy

Once the coffee has finished brewing, remove the filter and dispose of it alongside the grounds.

We always recommend trying to buy compostable filters so you’re not sending them to landfill. There are also lots of creative ways you can use your spent coffee grounds like in your garden, as a facial scrub, or to help with odors in your fridge.

Now, all that’s left is to sit back, relax, and enjoy your beautiful, crystal-clear coffee that is bursting with flavor.

You can, of course, opt for pre-ground coffee. But we’d really only recommend it when you’re in a bind. Coffee loses freshness within 15 minutes of being ground and, with a brewing method like pour over, the quality and flavor of your coffee really shine through. So, if you put poor quality in you can really only expect poor quality out. 

It doesn’t matter what type of coffee grinder you use, it should come with instructions indicating what setting to use for Chemex coffee brewing. Whilst these settings might not be perfect, they’re certainly a good place to start. Just on the off-chance you already know the specific size of each setting on your grinder, somewhere between 800-1000 microns will be perfect.

Don’t panic if your cup of joe isn’t perfect on the first go. It may take some trial and error to find exactly the right coffee-to-water ratio and size of coffee grounds for you. Just keep the following ‘rules’ in mind:

If the coffee from your Chemex is too bitter then it’s over-extracted and you need to use a coarser grind. If it is very acidic and thin then you need a finer grind size.

Within a couple of attempts, you should have your ideal Chemex coffee ratio and grind size nailed down. And, in the meantime, it’s fairly forgiving (especially when compared to the Hario V60.)

These “cups” aren’t mug-sized, like how many cups you are likely to drink, they are 6oz. So you can work out roughly how much coffee you need and go from there.

So, if you need to fill two 12oz mugs, then you’ll need at least a 4-cup capacity Chemex to brew all the coffee you need.

You can buy a Chemex in 3, 5, 6, 8, 10, and 13-cup versions of their famous coffee maker. Although the 5 and 13-cup versions are only available from their more expensive “hand-blown” range.

Obviously, you don’t need to brew to full capacity each time – you can brew your 4 cups in a 6-cup Chemex. But it’s pretty hard to brew 6 cups in a 3-cup Chemex without making a mess!

From there, you can adjust your coffee-to-water ratio, and grind size to get your perfect pour over coffee.

Whilst it may be a little more involved than your usual daily coffee routine, don’t be put off. Compared to other types of coffee maker, it’s very easy to use so you will be enjoying a delicious Chemex brew in no time. 

Even when you’re new to the pour over game, it will still be a massive step up from automatic drip or filter coffee machines. Plus, it’s an iconic, beautiful brewer to look at – every coffee fan should have one in their collection.

Matt Woodburn-Simmonds

Matt's coffee obsession started in 2006 when working as a Barista. A tendency to turn up to work hungover kickstarted his coffee journey which quickly turned into a love affair. As he moved on to work as a Restaurant Manager and Sommelier, the obsession continued to grow. Now, his passion is helping others to enjoy better coffee at home.