Coffee Grind Sizes 101: An Easy Guide

Your best friend is in Panama on vacation, and she just sent you a whole-bean, 250-gram pouch of the best Geisha coffee.

You have only ever read about this ‌coffee variety. You know Geisha coffee has always sold for big money and consistently wins top marks in the Best of Panama competition.

It's so remarkable that, in 2019, an independent coffee farm in Panama produced Geisha coffee that sold for USD 1,029 a pound. That's more than a thousand dollars for a small 454-gram bag!

All that expectation of greatness can cause undue pressure, of course. You know you must prepare it carefully and correctly. After all, you can't afford to waste such excellent coffee.

One of the critical components of making great coffee is grinding the coffee beans to achieve a correct and consistent grind size.

Why Particle Size Is Important in Coffee

Particle size is important in food science. For instance, it affects how much material you are using when relying on volumetric measurements, since particle size affects bulk density.

In coffee, particle size matters because surface area is a function of particle size. Specifically, the smaller the particles, the greater the specific surface area of coffee.

Why is surface area crucial? The greater the coffee surface area, the greater the area exposed to water. Likewise, the finer the grind size, the more packed the particles are, and the less quickly water can move between particles, increasing the amount of contact between coffee and water even more.

In contrast, the specific surface area gets smaller with larger coffee particles. Thus, there’s less surface area exposed to water. Since water can move quickly between coffee particles, contact between the water and coffee is further minimised.

The amount of contact between the water and coffee is relevant because the more there is contact between the two, the more flavours the water can extract from the coffee.

The flavours you enjoy in your cup of coffee are a mix of compounds such as caffeine, tannins, carbohydrates, oil, and proteins. Naturally, the more contact between coffee and water, the more compounds water can dissolve and the more flavour it can extract from the coffee.

Is More Water-Coffee Contact Preferable?

The greater the contact between water and coffee, the more flavours water can extract from the coffee. This is not always preferable, however. Overexposure can lead to the extraction of undesirable bitter flavours from the coffee.

Likewise, underexposure is not ideal. There must be sufficient contact between water and coffee. Underexposure can lead to the extraction of acidic and sour flavours, but none of the dark, deep and rich coffee flavours.

The key, therefore, is to control the extraction process. One of the ways you can do this is to ensure you are using the correct grind size for your chosen brewing method.

Particle Size Consistency

Make sure that you have consistent particle size when you brew coffee. Grind size consistency ensures a uniform rate of extraction from every coffee particle.

When the particles are consistent in size, none will be over-extracted (when the particle size is smaller than ideal) or under-extracted (when the particle size is larger than ideal). Thus, your cup of fruity coffee blends (e.g., your Colombia Frozen Cherry) will not become a mix of undesirable, bitter flavours from over-fine particles and sour notes from oversized particles.

Thus, unless your grinder provides a perfectly consistent output every time, ensure particle size consistency by using a coffee sifter.

Which Grind Size Should You Use?

You are, of course, free to experiment on which grind size gives you the best results. Tweak your go-to coffee recipe, and experiment with various particle sizes. This way, you will ‌find the grind size that best suits you and your palate.

You can, however, use the following guidelines. The information below provides particle size recommendations according to the coffee brewing method.

• Extra Fine

Extra fine coffee particles are 100 micrometres or 1/10th of a millimetre in size. Ground coffee this fine feels like flour. This particle size is ideal for making Turkish coffee which is brewed by boiling.

• Fine

Fine coffee particles are 300 micrometres and look like caster sugar or fine granulated sugar particles. This is the grind size recommended for making espresso using an espresso machine.

• Medium-Fine

Medium-fine coffee has a particle size of 500 micrometres and looks somewhat like table salt. Use this to make coffee using an AeroPress, a Moka pot, a syphon brewer, or a pour-over cone.

• Medium-Coarse

Medium-coarse coffee particles look like fine sand and are 750 micrometres in size. This is the standard size recommended for use with drip coffee makers and for making pour-over coffee.

• Coarse

Coarse coffee is 1 millimetre with particles that look like coarse sea salt. This is the size to use with percolators and your French press.

• Extra-Coarse

Extra coarse coffee looks like rock salt and has a particle size of 1.5 millimetres. This is the recommended grind size for cold brewing methods.

Grind Size Is Key

If you want the best-tasting coffee, mind your coffee particle size and ensure its consistency. 

Your Geisha coffee — or whatever superb single-origin coffee you have — will be wasted if you brew it haphazardly and without checking the grind size.