Why Is A Cup Of Coffee Only 6 Ounces Instead of 8?

Why Is A Cup Of Coffee Only 6 Oz

In the business of coffee, there is a set measurement that most people, coffee bean sellers, and coffee machine manufacturers among others adhere to.

This is the 6 ounce metric for a cup of coffee that is almost a universally understood agreement across the world.

Even if it is not quite set in stone, the unit has found its way as an accepted truth in the lives of coffee drinkers everywhere

Questioning The Norm

The number 6 ounces has become permanently linked to a coffee cup over the years. It is considered a standard for the industry and has made itself a true staple of the beverage that can not be denied.

And, while it may be common knowledge, many of these coffee lovers want to know the reason for the measurement.

After all, it would grow to become synonymous with coffee roasts globally. Because of this, it has lead to some having inquiries about the logic behind it.

So why is a cup of coffee measured at only 6 ounces?

The Truth Behind the Number

Behind the question, lies a varying answer that relies on a number of factors, both from the past and present. This is because of an accepted rule among individuals everywhere that 6 ounces is a fact of nature. Some of the variables that the measurement was founded and still hinge on are:

  • In the medical profession, 6 ounces has been deemed the approved amount for nutrition purposes. Field experts have made the decision that 6 ounces/100 milligrams are the ideal quantity for the average person. It is shown to balance the benefits of caffeine with the nutritional portioning needed.
  • Differences in the metric system internationally have lead to 6 ounces being a standard in most countries such as the US and Japan. This is because of the conversion issues that arise from translating the values across boundaries and borders as countries vary in their own definitions of a “cup”.
  • Along the way, most coffee machine manufacturers have also declared 6 ounces to be their mechanism’s default. It was done for a few reasons including to instill a universal unit that could be applied in most or all situations. It makes the process easier and gives the manufacturers a relied upon base to start within their production of the various items they create.

So all of this has to make you wonder something else:

How Many Ounces Do Coffee Makers Hold?

The amount of ounces in a cup of coffee and the amount of ounces in a standard cup measurement often differ as we’ve discussed above. Therefore, it is important to know how many ounces a coffee maker holds before purchasing.

A Cup of Coffee VS. Standard Cup

A standard cup measurement measures eight ounces. A cup of coffee can measure anywhere from four to eight ounces and frequently 6oz is the norm.

You may see coffee equipment companies listing the cup capacity of their machines in the product description. This cup capacity does not guarantee that it brews eight ounce cups or even six ounce cups.

This cup capacity guarantees that it brews this given amount of cups by their cup measurement.

The Math

For example, say a coffee maker you are interested is listed as a 12 cup brewing machine. If we multiple eight ounces by 12 cups we would end up with a carafe that can hold 96 ounces.

However, if the company sets their measurement for a cup of coffee at 5 ounces, the solution looks quite different.

8 oz X 12 cups = 96 ounces

5 oz X 12 cups = 60 ounces

Therefore, the coffee maker actually holds 36 ounces less than what the standard cup measurement would reveal.

Why Do Coffee Makers Do This?

Well, the short answer in my opinion is money.

The long answer is a machine that brews 12 cups compared to 8 cups is a lot more competitive in a slightly saturated market. You can sell a bigger capacity machine for more than you can a smaller capacity machine.

There are a lot of coffee equipment brands in the world, and this mathematics illusion can sometimes give them an edge on potential competitors who stick by the standard cup measurement or over those who don’t inflate their reservoir capacity as much.

How Do You Know How a Certain Equipment Company Measures?

The easiest way to determine what measurements a particular coffee maker you are interested in abides by is to check the specification sheet often included online in the maker’s description.

This sheet is also often included on the back of the coffee maker’s packaging if you are shopping in person (but not always).

On this sheet there should be a listing for cup capacity and another for volume.  To find out how ounces the machine measures as a cup, we simply have to divide the machines volume by its cup capacity.

More Math

For example, if the machine’s stated cup capacity is 8 and the machines volume is 1.5 quarts per packaging materials, then the machine abides by a cup measurement of 6 ounces.

1.5 quarts = 48 ounces

48 ounces / “8 cups” = 6 oz per cup

Following Up

Keeping all that in mind, 6 ounces remains the most common unit for a cup of coffee, and will probably remain in that state for the foreseeable future. It is seen in so many places from in-home coffee makers to even the businesses such as coffee shops and restaurants that serve it.

Likely the ingrained number will stay prominent for years to come with the way it has been used for everything coffee related including the manufacturing and selling of the beverage.

One thing is certain through all of this, coffee will continue to be a sought after drink that is enjoyed by all people – no matter the serving size.


Aubrey, A. (2006, September 28). Coffee: A Little Really Does Go a Long Way. Retrieved from https://www.npr.org/2006/09/28/6155178/coffee-a-little-really-does-go-a-long-way

Brian Mounts

Head blogger, editor, and owner of "Top Off My Coffee", a website that has been educating readers about coffee brewing techniques and equipment since 2012.

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