The best grind size for a moka pot is slightly finer than a grain of table salt but more coarse than ground espresso. A moka pot’s pressurized brew method requires a finer grind because it needs to extract more quickly. Buy an espresso grind if you’re buying pre-ground beans.

Grind size is probably the most important factor for brewing tasty moka pot coffee. This article will help you achieve the perfect moka pot grind every brew.

Why is finely ground coffee best for moka pot coffee?

Finely ground coffee is important for moka pot coffee because it has a short extraction period of about 1-2 minutes. Drip coffee takes about 3-4 minutes to brew.

This shortened extraction duration allows for a smaller degree of error when achieving the right amount of extraction. Coffee needs to be extracted more quickly so a finer grind with a larger surface area is necessary.

Coffee experts agree that an extraction of between 18-22% is ideal in bringing out the fresh, sweet and fruity characteristics while minimizing the bitter and astringent flavors.

We wanted to test for ourselves how grind size affected moka pot coffee, so we conducted a little experiment:

Our moka pot grind size experiment

We made three 100ml moka pot coffees with three different grind sizes – a coarse, medium and fine sized grind.

We brewed each batch using the same water temperature and brewing method.

We then blind tasted the three cups and discovered that the fine grind tasted best. It was the cup with the sweetest and best taste. The medium and coarse grinds were excessively sour.

The coarse grind had almost no redeeming characteristics and was borderline undrinkable.

The image above shows the approximate grind size that we found worked best for our moka pot brew. Notice the fork prongs and grain of table salt on the right for size comparison.

We found that the ideal size was slightly smaller than a typically grain of table salt but more coarse than an espresso grind.

Why is moka pot coffee finer than drip coffee?

Drip coffee used gravity to pull water through a bed of ground beans. This process takes about 3-4 minutes for an average single serving.

Because the drip coffee extraction period is longer, the beans must have a more coarse grind or else they will over extract and cause a bitter taste.

Best pre-ground coffee for moka pot coffee

Pre-ground espresso beans are the best choice for moka pot coffee because it has a finer grind. Pre-ground beans for drip coffee are too coarse and will cause your moka pot coffee to taste sour and acidic.

The sweet and tasty flavors you enjoy happen at that sweet spot of extraction. Those flavors will not be extracted quickly enough with a moka pot.

Therefore, a more finely ground espresso blend will produce a better tasting moka pot coffee. Pre-ground espresso beans are often a little too fine for moka pots so your coffee may taste a little bitter and astringent.

Many people believe moka pot coffee is the same as espresso. They have similarities but have some key differences, including grind size.

Problems with using coarsely ground coffee in a moka pot

Coarse coffee beans will cause the moka pot to brew a sour and acidic tasting coffee. This is because the sugars that give coffee its pleasant taste disn’t have a chance to dissolve into the water during the brewing process.

Here’s why:

Coffee beans have different organic compounds that range in molecular complexity. When coffee grounds are added to water, the simplest compounds dissolve first. These are the fats and acids that add some texture and sour notes to the coffee.

Next, the simple and complex sugars start dissolving. These are what mostly give coffee its pleasant taste. The slight sweetness and fruity flavors extract here.

Lastly, the complex organic fibers are dissolved. These are what makes coffee taste bitter and astringent.

Coarsely ground beans have a smaller surface area, which reduces the speed at which extraction occurs. Because each coffee brewing method is a little different, they require beans to be ground at different sizes to achieve an optimal extraction rate.

Problems with using finely ground coffee in a moka pot

Coffee beans that are too finely ground will cause moka pot coffee to taste excessively bitter and astringent. This is a result of the complex coffee bean fibers extracting when they shouldn’t have a chance to.