How Much Does a Coffee Bean Weigh: Math Made Easy

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How much does a coffee bean weigh

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I suck at math. True story. 

Seriously, I would be lost with anything more complicated than simple multiplication without the help of a calculator or Google.

So when I tell you that I persevered to overcome my phobia, I hope you can appreciate my suffering. But that’s not why you’re here, is it?

A typical coffee bean weighs around 133 milligrams; however, variations are expected due to multiple factors.

What kind of factors? Well, read on to learn how your coffee beans are affected and marvel at my super-nifty math skills!

Why Should You Care About the Weight of a Coffee Bean?

why do i care about the weight of a coffee bean
The weight of a coffee bean has a purpose if you take your brewing seriously.

Hold the brakes for just a second. You’ve already gotten your answer and could go about your business.

But for those who stumbled upon this page, you’re probably asking why the weight of a coffee bean is so important. Does it really deserve its own 1000-word dedication?

Well, yeah.

The simplest answer is that weight is directly tied to the quality and outcome of your brew.

How you choose your brew method will alter the caffeinated content or help you determine the grade of your sourced coffee.

I cover more on this when I discuss the caffeine content of the different roast types.

Now back to your regularly scheduled program!

How Much Does a Single Bean Weigh in Grams?

As I said earlier, an average bean weighs 133 milligrams. The conversion calculation to get grams from milligrams is to divide the number by 1000.

how much does a single bean weigh in grams
Some basic unit-of-measure conversions will be required when dealing with weights and volume.

So a single bean weighing 133 milligrams, divided by 1000, equals 0.133 grams.

But how can I be so sure? Why should you trust me? Or, as every single one of my math teachers would say, “show your work!

How Do You Calculate the Weight of a Coffee Bean?

The best way to calculate the weight of a coffee bean is to measure them with an electronic scale.

Since they are so small, you’ll need multiple coffee beans to measure simultaneously. Otherwise, weighing a single bean won’t register on most scales.

Below are the steps to follow for weighing your beans. The beans in my pictures are Kicking Horse Smart Ass coffee beans. And I highly recommend them if you’re looking for a fuller taste.

Step 1

Turn on the scale and ensure it’s set to grams, with nothing on the surface. The reading should be 0.

Step 2

Place a single bean on the scale. You should see that the display still reads 0.0 grams.

single bean on scale
Notice the 0.0 grams shown for a single bean.

Step 3

Add a couple more coffee beans to the scale until you get a weight reading above zero grams.

In my case, the scale showed me a total weight of two grams, 2.0 to be exact. So how did I calculate .133 grams for a single bean?

many beans on scale
The best way to find the weight of your coffee is to measure it in bulk.

Well, my little solar-powered calculator made this bit of math possible.

Step 4

Count the number of beans on the scale and divide the total weight by the number of coffee beans.

I had 15 beans weighing two grams.

average calculation
When using the calculation for finding averages, coffee beans typically register at .13 grams per bean.

2/15 = .133 grams, or 133 milligrams.

Simple, right? You may be underestimating my disdain for arithmetic.

What is the Average Size of a Coffee Bean?

During that exercise of mine, you may have thought, “well, Chris, that’s just a couple of coffee beans from the gazillion out in the world. What about my beans or maybe the coffee I’ll buy this weekend?

Too true. 

A lot of factors play into the weight or volume of a coffee bean. I said that, didn’t I? That must mean there are more answers than just .133 grams for a single bean.

Yes, but less often than you think.

The average size of a coffee bean is 10 millimeters (mm) long and 7 mm wide.

average size of a coffee bean
You may find alternative answers, but 10 mm by 7 mm is an accepted standard-size coffee bean.

If we assume that to be true, then most coffee beans will share similar dimensions on average and thus weigh about the same.

Forget about my beans for a second. How about we look at some other real-life examples outside my own kitchen?

Luckily, the Asian Journal of Applied Sciences put together a comparative study of changes to coffee beans during the roasting process.

This study examined aspects of Arabica and Robusta beans at three roasting levels; green coffee beans (GB), roasted beans until several minutes after the first crack (RB1), and roasted beans until several minutes after the second crack (RB2). 

roasting coffee beans at different levels
The longer the roast, the lighter the bean.

Thirty samples were used to better understand the changes the beans experienced. And as you might guess, the measured dimensions varied for the six types of beans (3 for Arabica and 3 for Robusta). The Arabica beans were generally larger, but that’s not surprising.

By using the same equation earlier, I add the total average length of all beans and divide by six. I do the same for the width and get the resulting 10 mm in length and 7 mm in width.

It’s not an exact science, but averages are the way to go when dealing with the kind of numbers that exist with coffee beans.

FAQs About Coffee Bean Weight

Fact or fiction: What other weight-related questions about coffee can I answer for you?

Do Coffee Beans Weigh More Than Ground Coffee?

In theory, coffee beans weigh about the same as when ground coarse or fine.

weight of coffee ground or whole
With the perfect conditions, the weight of coffee as a bean or ground will be the same.

I won’t guarantee that this will be true for your own test because circumstances can affect the weight positively or negatively. Can you guess what these circumstances are? It may be simpler than you think.

You see, if you weigh 10 grams of coffee beans and then grind them up before you measure again, you could get a result of more than 10 grams.

If your grinder has yet to be cleaned, loose coffee grinds from a previous brew could mix with the newer beans you just crushed.

havent cleaned my grinder yet
A dirty grinder can contribute to weight variations in coffee from bean to grind.

Even if your grinder has been cleaned, check for leftover grinds stuck against the wall of your grinder. These leftovers could be enough to cause a weight discrepancy.

Does Roasting Affect the Weight of a Coffee Bean?

Roasting definitely affects the weight of a coffee bean since the longer a bean is exposed to heat, the more moisture is lost. This causes the coffee bean to lose a considerable amount of weight.

Not only is time a factor in coffee bean weight loss, but the roasting method can also play a role.

How Many Grams of Coffee Beans Per Cup of Coffee?

According to the National Coffee Association, the recommended amount of coffee per cup is 10 grams or 2 tablespoons.

how big is the average cup of coffee anyway
The average cup of coffee ranges from 6 to 8 fluid ounces.

Of course, this number can and will change based on brewing methods or individual tastes. But it’s good to remember that the NCA recommends this with a 6-fluid-ounce cup of coffee in mind. 

Many coffee drinkers, especially Americans, consider 8 fl oz a standard cup of coffee. You’d want to measure closer to 12 to 14 grams of coffee in this case.

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