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what's in a tablespoon: converting volume to weight in ground coffee

tldr;

How much does a tablespoon of coffee weigh?

The finer the grind and the lighter the roast, the heavier the tablespoon, but for the typical grind you’ll get from the grocery store and a medium roast bean, a tablespoon weighs somewhere between 4.45g (coarse) to 4.75g (fine). Use this if you’re trying to move from a volume-based recipe to a weight-based recipe.

Overview

If you’re trying to up your coffee game, there are lots of complicated devices and techniques that you can use to really improve the quality of your brew. But one way to introduce a little bit of consistency into your brew is by measuring out your coffee and water by weight, not volume. Lots of your simpler recipes use volume measurements, like a tablespoon of coffee grounds or a cup of water (for reference, a cup of water is 236.6 grams). Getting the precise amount of coffee grounds is critical to an accurate water-to-coffee cold brew ratio and a tasty cold brew.

Which is great if everyone’s tablespoon was perfectly leveled off with the same ground coffee, but we humans are imperfect. And a “tablespoon for me” is a bit different from the “tablespoon” that my wife uses. This matters because a heaping tablespoon vs. a leveled tablespoon can vary the volume and weight by 30-40% of a leveled tablespoon. 

Grind size introduces another rub: a tablespoon of finely ground coffee is not the same as a tablespoon of coarsely ground coffee: the coarser the grounds, the lighter your tablespoon will be. It’s easy to think of this rule with finely ground coffee and the coarsest coffee you can imagine: unground coffee beans. If you have beans in your tablespoon, there’s lots of space in between them as they awkwardly sit on top of and next to each other. Whereas with fine coffee, the particles are so much smaller that they pack in much better, and can fit more “coffee” into a tablespoon. 

The Experiment

This experiment was a simple one: I wanted to see how the weight differed based on grind sizes for a unit of measure typically used in recipes: the tablespoon. I measured out a level tablespoon of coffee ground at three different settings: fine, autodrip, and coarse. Why those three settings? 

  • They reflected a nice range of settings that you could grind at in a standard, supermarket coffee grinder

  • They reflect the three brewing methods that are most likely to found in someone’s house (french press, pour over, automatic drip)

Fresh Ground Coffee

Fresh Ground Coffee

We used a medium roast coffee (Allegro’s Beantown blend, to reflect our Boston roots). It’s important to note that darker roasts tend to weigh less than lighter roast, as the longer roasting tends to evaporate more of the residual liquid content of the beans (Homegrounds has a nice article which talks about this).

All tablespoons weren’t packed but were leveled, to ensure consistency.

The Results

While there was some deviation in the repeated measurements of each grind, there was a clear difference in the weight of each grind size’s average tablespoon. As expected, the finer grind was heavier, as the smaller coffee particles could fit more tightly together. Coarser ground coffee weighed less, as there was more space for air in between each particle. 

Tablespoon+Readings+by+Weight.png

The difference between a coarse and a fine drip tablespoon is 0.3 g - a 7% swing. While not the same as the difference between a leveled mound and a heaping mound, it is enough to start impacting the ratios that you’re trying to fix. The standard deviation in the readings is a takeaway itself, and shows the challenge of trying to measure with volume: even an experiment that is trying to solve for a precise volume isn’t able to consistently get the same volume / weight. 

Summary

The ground coarseness impacts the coffee weight, which will impact the actual ratio - and flavors - that you’re getting from your recipe. While the difference isn’t massive - only 7% difference from coarse to fine, it’s certainly material depending on how exact you’re trying to control for the flavors. This will be critically important in our research as we go deeper in exploring what effects different variables in the brewing process have on the end product, coffee. 

For those looking for a scale, I love the Hario V60 Drip Coffee Scale. It’s sleek, it has a timer if you want to brew your pour over even more precisely, and it weighs to a high degree of accuracy. In this photo, I’m using the Taylor 1250 BKT Scale, which I love because it goes out to 0.01 grams (super useful for research). If you’re fancy, the Acaia is basically top of the line.

When in doubt, finding a recipe that uses a cold brew ratio measured in weight is the safest way to go. 

(ed. this was originally posted on April 16, 2020)