How Big Is a Coffee Cup? The Answer Isn't Obvious

I hate to break this to you, but a coffee cup on your drip coffee maker may not be as big as you think it is.

Perhaps when you bought your 12-cup machine you thought the cup in question was the same 8-ounce cup recognized by Google, your grade school math books, and the measuring cup in your kitchen drawer.

I’m sorry to tell you, but this is very much not the case. I test coffee machines for a living and can attest that a “cup” defined by makers of drip coffee machines has nothing to do with the measuring cup you'd use while baking cupcakes. It also bears little relation to the size of an average coffee mug.

Instead, a coffee “cup” is a weird relic of a different time. It turns out to be a strange and elusive measurement, somewhere between 4 and 6 fluid ounces, as little as half of a standard US measuring cup. Often, a “cup” turns out to be metric. And its precise size will depend entirely on the whims of whoever makes your coffee machine.

“There’s really no standardization for anything in coffee,” says sales associate Sean Jemison at esteemed Portland, Oregon, coffee supply shop Clive Coffee.

The Dutch-made Technivorm MoccaMaster, one of WIRED’s consistent favorite coffee makers and a perma-guest on our buy-it-for-life guide, marks out a standard cup of coffee as 125 milliliters—just a little over 4 ounces. This means a 10-cup MoccaMaster will actually make just four or five mugs of coffee. This same small cup size holds for Sweden's lovely-looking Aarke Coffee Maker.

Meanwhile, an old Mr. Coffee drip machine demarcates a cup as 5 ounces, the same measure used by the much fancier Ratio Four coffee maker (8/10, WIRED Recommends). But a K-Cup won’t get out of bed for less than 6 ounces.

An average American coffee mug, meanwhile, runs between 8 and 12 ounces, notwithstanding those huge Yeti travel tumblers. So what gives? Why is coffee so weird? Is this a 10-hot-dog, 8-bun situation? Here’s the rundown.

The Mr. Coffee Revolution

It's normal, in these times, to be suspicious. And so I forgive you if you assume chicanery. Online coffee forums are littered with commenters who accuse manufacturers of coffee makers of flat-out doctoring the size of a “cup” in order to mislead potential buyers.

Maybe, maybe not. But the small size of a cup probably has a lot more to do with the history of coffee in the latter half of the 20th century. It turns out that the size of a coffee cup hasn’t really changed much since the invention of the electric drip coffee machine. It's the coffee drinkers who changed.

Mariella Giovannucci Esposito, the 73-year-old owner of century-old coffee and housewares store Fante’s Kitchen Shop in South Philadelphia, watched this evolution in real time after she began working at the store in 1971. She took over the shop a decade later, expanding its coffee repertoire.

In the early ’70s, Esposito says, Mr. Coffee “revolutionized” coffee drinking in this country, for better or worse. People used to mostly make coffee with percolators. Drip coffee existed, but it wasn’t yet as popular or as easy to make. But with Mr. Coffee’s new and jaw-droppingly automatic drip coffee machine, the way people drank coffee at home changed entirely.

The first Mr. Coffee was a phenomenon, despite costing the equivalent of more than $200 today. But it was new, exciting, and easy to use, and it made a lot of coffee at once. By the end of the 1970s, Mr. Coffee controlled fully half of the American coffee maker market.

The standard serving size that Mr. Coffee arrived at was a 5-ounce “cup,” about the size of a British teacup. Though this may seem small now, it actually did correspond to the size of the cups people used for coffee at the time, Esposito says.

It’s also the size that Esposito, a native of Italy, still considers “reasonable.”

Blame It on the Mermaid

You can demarcate coffee cups in America into two periods: B.S. and A.S.

Everything began to change in the late ’80s, Esposito says, somewhere around the time a former Xerox salesman named Howard Schultz decided to take a Seattle-founded coffee shop onto the national stage. After Starbucks, coffee cups got bigger.

“They created their own language for all of their drinks and sizes and everything. So a ‘small’ to Starbucks is really kind of like a ‘large’ everywhere else,” says Jemison, the Portland coffee machine salesperson.

“From my memory, until Starbucks, most of the coffee drinks were reasonable. I mean, the cups were a reasonable size,” Esposito confirms to WIRED. “And then the larger sizes were introduced.”

It’s probable that mug inflation had already begun prior to the Venti diaspora. But as Starbucks expanded in the ’90s, Esposito says, other local cafés felt the need to compete. The café cups got bigger, and so did her customers’ perceptions of how big a “cup” is.

Now, when customers arrive at Fante’s to get a coffee maker, she has to stop to explain that a coffee-machine cup doesn’t correspond to a measuring cup, and it also doesn’t correspond to the cup her customers actually drink coffee out of.

“When people come in and ask for a coffee maker and they look at ‘12 cups,’ we automatically explain, ‘That's not the size of, you know … 12 of your cups,’” she said.

Just Double It

But even though we drink coffee cups about twice as big as we used to, coffee maker companies have no particular incentive to change their cup sizes. Doing so would make their machine look half as big as it used to be, and half as big as competitors’.

The math, instead, falls on you: You'll need 2 “cups” for one serving, at least if you drink out of a 10-ounce or so coffee mug that’s now considered standard. It’ll take 4 cups, however, to fill a Yeti mug or one of those Stanley beer steins some folk like to drink coffee out of these days.

Nonstandard cup sizing can often mean you'll need to read the user manual carefully to discover how much coffee to use. Most makers do come with a dosing spoon, for a loosey-goosey approach to coffee ratios, and may also detail a recommended weight of coffee per machine-demarcated cup of water.

But if you happen to be a precise person who wants to measure out your coffee to exact specifications by weighing your beans or coffee grounds down to the gram? You’re going to have to get out your coffee machine’s manual and read the fine print to discover the “cup” size your machine is using. This may be difficult to figure out, in some cases.

As a rule of thumb, American-made machines do tend to have 5-ounce cups. And a 5-ounce cup corresponds to about 140 grams of water. To attain the 17:1 ratio of water-to-coffee often touted as ideal by the international Specialty Coffee Association, each 5-ounce cup would require about 8 grams of coffee.

Your 10-cup machine, then, will be happiest being poured through about 80 grams of coffee grounds, or nearly 3 ounces of coffee. You’re welcome. And I’m sorry.

For more coffee advice, check out our guides to cold-brew coffee makers, espresso machines, automatic latte machines, and coffee gifts.