When we think of making coffee, we usually focus on getting great coffee beans. And make no mistake, great coffee will always begin with high quality beans.

But to have truly amazing coffee, you need to get down to the (coffee) grounds, and match the right grind size to the right brew method.

The science of coffee grounds is part math, part chemistry, and 100% taste. So, we’re going to break down the different sizes of coffee grounds and what brew methods they work best with – all to support your quest for the yummiest, most flavorful coffee possible. Let’s get going.

THE MATH 

The biggest reason coffee grind size matters is because it changes the surface area of the coffee itself. A single coffee bean has a small surface area, and even if you put a handful of beans into water, only a small percent of the water would come into contact with the beans, and you definitely wouldn’t call the result “coffee.”

(Did we try this ourselves? Maybe… and did the result make us sad? Yes.)

So, when you grind coffee beans, you’re creating more coffee surface for the water to interact with.

And different grind sizes result in different surface areas. Coarsely ground coffee has the smallest surface area, and finely grind coffee has the largest surface area.

Combine surface area with the other main variable – time – to get a sense of which grind size is best for which brew method. For instance, a coarser grind is better for brewing methods that take more time; think cold brew and French Press. Pour over methods only allow 2-4 minutes for the water to contact the coffee, so they work best with a finer grind.

THE CHEMISTRY 

Here’s a question: do you know what actually makes coffee, coffee? After it’s brewed, what is left of the coffee beans in the water? The answer: coffee compounds! There are hundreds of compounds in roasted coffee beans, and when you brew coffee, you’re transferring those compounds into the water to make a delicious drink. If you want to know more about these compounds, you can read up on more coffee science.

Using the right grind for the brewing method produces an optimal transfer of these compounds into the water. Too large a grind for the brew method and you’ll get weak coffee, because not enough of the compounds will be transferred. Too fine a grind for the brew type and you’ll stronger, bitter coffee.

SHOULD YOU BUY PRE-GROUND COFFEE? 

Many people buy pre-ground coffee, and we get it! It’s convenient and it’s one less thing to think about in the morning. But, be aware, this has two main disadvantages.

The first is that you can’t control the grind size, and so you just have to make do with whatever the standard grind size is. Usually, this is a medium-fine grind designed for automatic drip machines.

The second disadvantage has to do with freshness and flavor potential. The coffee compounds (aka the source of coffee’s flavor!) are protected by the coffee bean in its whole form. And although most coffee bags have an airtight seal when unopened, the ground coffee loses its freshness and flavor faster than whole coffee beans. 

It’s extra half minute or so whenever you make coffee, but it’s absolutely worth it in terms of coffee freshness and flavor!

COFFEE GROUNDS & BREW METHODS 

Now that you know why grind size matters, here’s a chart of some popular brew methods and the optimal grind size for each method:

Once you’ve mastered coffee grinds, have fun experimenting with different brew methods. If you don’t have a grinder yet, check out our favorite coffee grinders, including some affordable options!

HIGH QUALITY BEANS, ROASTED TO ORDER?

With a subscription to Atlas Coffee Club, you can get specialty grade, single origin beans roasted to order and delivered on your schedule. Each month, you’ll discover a new coffee from a new country – and you’ll have access to a team of Coffee Tour Guides to answer any brewing questions you might have (or just talk coffee 🙂 )