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Coffee grind size: Why it matters and what you should be using

Grind size can be the difference in a delicious or an unpleasant, bitter cup of coffee. Learn why grind size matters and which setting you should be using for your coffee at home.

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Taylor Martin/CNET

Making better coffee at home is spending a little extra time on a few, simple steps, such as using the correct temperature water, weighing coffee instead measuring by volume, and grinding your own beans on the spot.

Of everything you might encounter when brewing at home, grinding coffee is arguably one of the most crucial steps, as grind size alone can dramatically change the taste of your cup. Grind size and consistency can be the difference between one of the best cups you've ever had and a bitter, undrinkable mess.

Discover how grind size affects your cup and which is right for your brew method of choice.

Why grind size matters

When it comes to grind size, there are three factors which make the biggest difference: contact time, extraction rate and flow rate. To put it simply:

  • The extraction rate of coffee grounds increases with a larger surface area.
  • To increase surface area, grind the coffee finer.
  • The higher the extraction rate, the less contact time is needed.
  • A finer grind can reduce the flow rate of water, increasing the contact time.

Knowing this, if you have a brew method with a short contact time, the grind should be finer. In an immersion brewer, which steeps coffee grounds in water for several minutes, the contact time is much higher and, thus, requires a more coarse grind than most other brew methods.

If the contact time is too high or the grind is too fine, it will result in an over-extracted brew which can be bitter. If the grind is too coarse or the contact time is too short, the coffee will turn out weak.

Finding the proper balance between the two will help in producing the best cup of coffee possible.

Different types of filters, pressure and temperature can also play a part in determining grind size, but most brewing methods operate between 195 and 205 degrees Fahrenheit (90.6 and 96.1 degrees Celsius) with little to no added pressure.

Which grind size should you use?

With an array of different brewing methods, knowing which grind size to use is crucial to getting the best possible cup.

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Taylor Martin/CNET
  • Turkish coffee calls for an extra fine grind size, similar to that of powdered sugar.
  • Espresso is a brewed through using pressure (approximately 9 bar) to force water through compacted coffee grounds. The contact time is very short, requiring an extra fine grind size.
  • The AeroPress is a popular single-cup manual coffee maker. It's similar to a French press in design and use, though users have come up with a laundry list of ways to brew. Recommended grind size is between medium and fine, depending on steep time.
  • Siphon brewers use pressure to force water into a chamber holding the coffee grounds. Once the steep has finished, heat is removed, which creates a vacuum in the lower chamber and pulls the water through a filter. This method calls for a medium-fine grind size.
  • Pour-over brewers come in an array of different sizes and shapes. While different brewers require varying grind sizes to control the flow rate of water, most pour over methods call for a medium to medium-fine grind.
  • A stovetop espresso maker or Moka pot is a coffee maker which uses steam pressure to force water upwards through a filter basket full of coffee grounds. The contact time is quite short, but the pressure (approximately 1.5 bar) is a bit higher than your typical manual brewer. It calls for a medium grind size.
  • A single-cup coffee maker, such as a Keurig or Verismo machine, is a drip brewer method, similar to the commercial drip brewers found in cafes. The contact time is fairly low, meaning it calls for a medium to medium-fine grind size, comparable to that of table salt.
  • Drip coffee is what you typically get from a cafe or coffee shop. It's made in large batches and contact time is dictated by a small hole in the bottom of the brewing basket, so recommended grind size varies between medium-coarse to medium.
  • The French press is an immersion brewer. Water is added to coffee grounds and allowed to steep for several minutes before straining out the grounds. This method calls for a coarse grind setting.
  • Cold Brew, unlike other brewing methods, is done at or below room temperature and takes between 12 and 72 hours. Due to the low temperature, the extraction rate is low, regardless of grind size. A coarse or extra coarse grind size is recommended, as it's easier to filter. A finer grind size will work just as well (with a slightly shorter steep time), but can cause the final product to appear a bit cloudy.

Of course, all the above recommendations are just that -- recommendations. They are subject to change based on preferences and slight differences in brewers. Getting the grind size exactly right requires some testing and tweaking.

If you feel your cup of coffee is a tad weak, try a slightly finer grind size next time. Or if the coffee tastes too strong or slightly bitter, test with a slightly larger grind size to see if it solves the problem.