Two tablespoons per cup. We have all heard it. It’s sort of the rough “golden ratio” when brewing coffee. Stick to the correct ratio of coffee to water and you will have a good chance of brewing something drinkable. I was recently asked on Quora (Hi, guys!) if, when preparing coffee, it made a difference if you were measuring ground coffee or whole bean coffee. I had a knee-jerk reaction but this got me to thinking. I decided to do a little experiment and here’s what I found.
Spoiler Alert: It does make a difference but it is a meaningless one! Two tablespoons of whole bean coffee, when ground, will take up less volume. But that’s not the important question to answer. What’s important is whether or not that difference will meaningfully impact your finished cup. Read on to find out how I changed my mind!
Not As Straightforward As I Thought
This should be an easy experiment to pull off, right? All I have to do is measure a scoop of beans with a volume of two tablespoons, grind them, and then measure them again. If there is a difference, well, there’s a difference. Both easy and peasy.
Well, my first “thing” was that MY scoop holds four tablespoons. No big deal but it was a thing and I felt like I should mention it.
Well, no… it was not as easy as I had thought. Well, my first “thing” was that MY scoop holds four tablespoons. No big deal but it was “a thing” and I felt that I should mention it. My first true stumbling block was my new-to-me grinder.
You see, I recently picked up a new grinder from a charity shop in Moreton-In-Marsh, a medium-sized village in England, a couple of hours outside of London. My beautiful wife found it for me. 😘😘
It is a stylish and very efficient grinder. The round base does present a small challenge. It has a slight disinclination to stay in one place when wedged against the strip on the stove. All-in-all, it was a nice upgrade from my old antique grinder. It does, however, have one other quirk in its design that comes into play for our little experiment.
You may notice that there is a small gap between the funnel part of the grinder and the business part of the grinder: The burrs that do the actual work of grinding. That gap is notorious for catching the bits of coffee that have chipped off the beans while grinding. The chips pop up out of the reservoir – some even make it all the way to the counter – and find their way into this gap. It is even large enough for entire coffee beans to get trapped inside. This is a variable that I wanted to eliminate as any coffee that did not end up in the final tally would lead to an inaccurate final measure of ground coffee.
So I decided to go old school.
The Mortar and Pestle
My wife picked up this mortar and pestle from Ikea and it was exactly what I needed for this mini-experiment. The coffee beans would go in, they would be ground by my hand, and other than a bit of residue left on the surfaces, all of the ground coffee would come out.
I did not just come up with this idea out of thin air; there is historical precedence for using a mortar and pestle to grind coffee. Until the invention of the coffee grinder in 15th-Century Turkey, it was the goto method. It is said that Beethoven insisted that his coffee be made with exactly 60 beans ground in a mortar and pestle. That’s attention to detail.
I measured a scoop of beans. The scoop has a volume of four tablespoons. I decided that half-a-bean over the lip would be a reasonable way to balance out the empty space between the beans on the top row.
I then poured them into the mortar.
And ground them.
And ground them.
It took a while, and quite a bit of elbow grease, to get the coffee to the consistency I use to do my morning pour-over. In the end, I made it but I will not be trading in my grinder any time soon.
Carefully making the transfer to the scoop, it became apparent that I had my answer. Grinding whole bean coffee definitely causes it to take up less volume than when it was in whole bean form. My intuition is that this is because the smaller particle size allows for smaller airspaces between the grinds. This makes sense to me and was what I had assumed from the start.
But Wait Just a Coffee Picking Minute
However, what if while transferring the ground coffee to the scoop I also packed it more tightly into the scoop? What if I didn’t pack it enough? This is a variable that I had not considered. I do not know if there is any way to come to a consensus on this. It will come into play in the conclusion.
So what, indeed. How does this information impact our morning cup of goodness? How is this making us better coffee makers? I decided that this called for a bit more analysis.
Weighing the Situation
The empty scoop weighed in at 12 grams.
My scoop of whole coffee beans weighed in at 14 grams.
Obviously, when finished, the ground coffee weighed the same.
When I added the small amount of ground coffee needed to fill the scoop, I ended up with the same weight. Hmm. That would seem to indicate that the mass of the extra coffee was negligible – or at least within the margin of error on my kitchen scale. It is nominally precise and at higher weights, it appears to be accurate.
The answer to the initial question, “Does ground coffee take up less volume than the whole beans before grinding” is a resounding yes. I measured a scoop of coffee, ground it with a mortar and pestle to minimize any loss and measured the ground coffee. It was clearly taking up less space in the scoop. I could have compacted the coffee considerably but I did not think that was in the spirit of the inquiry. For that matter, I could probably have lofted the coffee as well. It was interesting to note that the weight of the ground coffee needed to fill the scoop was negligible.
Let us remember that the underlying point of this exercise was to determine how best to measure coffee in order to make a good cup of coffee. As we have discussed, to make the best cup possible, you should use the weight of the unbrewed coffee, whether whole beans or pre-ground, not its volume. As I mentioned in my article The Proper Coffee to Water Ratio (Metric Style!), the correct ratio to use is 11 grams of coffee to 200 ml of water. My usual mug holds about 280 ml of brewed coffee (leaving room for cream, of course), so my scoop of ground coffee gives me the correct strength for my cup.
I am not some “supertaster” who can determine which side of the orchard the coffee was grown in. I am not the kind of guy who will settle for nothing less than Esmeralda Gesha in my cup. The scoop is “good enough.” And my takeaway is that the difference in taste you are likely to experience between a scoop of whole bean vs. a scoop of ground coffee is not worth the worry or the fuss. Just be consistent with the methods you use to prepare your cup, make adjustments as needed, and you will never be disappointed.
My final word on this: There is a difference between a tablespoon of whole bean coffee and the volume it takes up after being ground. But it is a difference that does not make a difference to your cup.