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Our coffee maker instructions often refer to a "cup" of coffee. These cups are whats marked on the side of the coffee maker showing how much water is in the reservoir. The instructions never define what a "cup" actually equates to. It appears to about 6 oz. An old coffee maker seems to also have had this definition of "cup". The coffee beans we got from the local coffee shop also have instructions indicating one scoop of beans per 6 oz cup.

To be clear -- Is a "cup" to a coffee maker always 6oz? and therefore it has nothing to do with the Imperial unit "cup" which is 8oz? Its more a notion of a typical serving size of coffee?

Martin Schröder
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Doug T.
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    Given the cultural variation in coffee preparation, it would be useful to make your context explicit. (I presume it's the USA, since you're talking about ounces, but one can never be sure). – Peter Taylor Jul 14 '12 at 19:31
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    My Keurig coffee make has markings for small, medium, and large cup. They are equivalent to 6oz, 8oz, and 10oz respectively. – smcg Jul 15 '12 at 03:35
  • And remember US and UK fluid ounces are slightly different. – staticsan Jul 30 '12 at 07:13
  • If you buy a boxed set of place settings, they come with these teeny little coffee/tea cups that collect dust at the back of your cupboard. For some reason, these useless things have become the standard size for coffee, even though no one uses them. – Chris Cudmore May 13 '13 at 20:52
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    Coffee Pots in the USA are pretty universally 5oz. This is true for the 1970s Mr Coffee brand maker I have in my closet as well as the Cuisinart we have at work. Fill the carafe to 12 "cups", then pour into a proper measuring container. You'll get 60oz, not 72oz. You're expected to serve in a 6oz mug with 1oz of head space so you don't spill. Here's some more info: http://www.jesrestaurantequipment.com/howcoffeecarafesizingworks – bobpaul Jul 22 '17 at 18:41
  • Can confirm @bobpaul's 5oz claim. I filled up my Black & Decker carafe once to the 8 line and once to the 10 line, emptied them out into my liquid measuring glassware and got 40oz and 50oz respectively. – Abe Voelker Oct 25 '17 at 15:26

2 Answers2

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Assuming you're talking about USA usage, you're correct, a "cup" is usually 6oz. In the USA, the standard size for a "cup" of coffee is 6oz, even though nobody drinks cups of coffee that small (12oz to 20oz is more common). For that matter, the size of a "cup" of tea can be 5oz or 6oz when the number of "cups" a teapot holds is listed; a "6 cup" teapot is only 32oz.

However, be careful how the word is used in American recipes. If a recipe calls for a "cup" of coffee, they are more likely to be calling for an 8oz cup, rather than a 6oz cup.

I can't find a clear reference as to where the unrealistic 6oz measurement for a cup of coffee started. Possibly the result of Mr. Coffee, but we're stuck with it as customary now.

However, even though a 6oz cup of coffee may be customary, specific coffee maker manufacturers may use different measurements on different models, including cups as small as 4.2oz. So don't assume unless you've checked.

Oh, and also note that the 8oz cup is American, rather than Imperial measurement. An Imperial cup is around 10oz, although you're unlikely to encounter this measurement in any recipe published after World War I.

Confused yet?

Reid
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FuzzyChef
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    Maybe the 6oz measurement started at the time when Americans still drunk coffee in that measurement, AFAIK the trend to ridiculously large drink sizes is a few decades old – rumtscho Jul 15 '12 at 11:08
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    The meaning of "cup of coffee" varies by country. I have a Technivorm coffee maker that is manufactured in the Netherlands. The markings to fill the water correspond to 4 oz per "cup of coffee". – Rick G Jul 15 '12 at 15:09
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    rumtscho, yes -- actually I'm guessing it dates to a time when there was a difference between "cups" and "mugs" and coffee "cups" were the round-bottomed ones which look like oversized teacups. – FuzzyChef Jul 15 '12 at 18:10
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    Also note that "oz" varies. An *imperial fluid oz* is 28.413 ml, whereas a *US fluid oz* is 29.573 ml. What's for sure is that if I want to make one cup of coffee, I put more water in the machine than the "1 cup" level. – slim Feb 06 '13 at 13:15
  • And this is why you generally want to find where it lists the volume in liters, as both cups and ounces may not be what you think they are. (although I seem to remember there being one review of an electric kettle where someone complained that the number of liters didn't correspond to the 'max fill line' of the kettle, so even that can be not what you expect) – Joe Feb 06 '13 at 18:51
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    I just bought a 3 cup French press. I brewed it according to 3 cups of coffee grounds for a 6 oz cup, and it turned out that the press considers a coffee cup to be 4 ounces! Today's coffee was particularly strong. So, the press makes 3 cups at 4 oz, 2 cups at 6 oz, and 1.5 cups by Imperial standards. Yuck! – Joe Plante May 18 '15 at 20:46
  • Wikipedia mentions the "cup" is 150 mL (5.07 fl oz) and "4 oz coffee brewed with 5 oz water" without any citation. My "5 cup" carafe filled up to the 5 cup water line with cold water is about 800 g heavier, so ~160 mL/cup – Nick T Nov 30 '17 at 16:35
  • Do you have a citation for “Federal regulation”? As currently written, that passage seems to be a random cliche slagging on the federal government, rather than anything that supports the answer. – Reid Oct 15 '20 at 18:27
  • If you read the sentence immediately before it, clearly not. Context is everything! – FuzzyChef Oct 15 '20 at 23:02
  • Here's a more extensive answer to the origin of the 5-6oz cup, from Coffee SE: https://coffee.stackexchange.com/questions/2317/why-is-a-cup-of-coffee-not-6-oz – FuzzyChef Nov 01 '20 at 01:22
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From The Professional Chef (by The Culinary Institute of America), p. 1165:

1 measuring cup holds 8 fluid ounce (a coffee cup generally holds 6 fluid ounces)

So indeed, the unit 'cup' is different from the standard coffee 'cup'. I wouldn't assume a coffee cup always to be exactly 6 oz, there might be variation from brand to brand. There shouldn't be any variation in the cup unit though.

Mien
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